wangle/service:ServiceTest: fix ASAN test

Summary:
```
      ☢ wangle/service:ServiceTest - Wangle.ClientServerTest 1.799s (FATAL)
Failed to find test summary. This test binary may have crashed mid-run. Full output follows:
Note: Google Test filter = Wangle.ClientServerTest
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from Wangle
[ RUN      ] Wangle.ClientServerTest
=================================================================
==2396362==ERROR: AddressSanitizer: heap-use-after-free on address 0x611000000568 at pc 0x000000481dfc bp 0x7fff7d9c2eb0 sp 0x7fff7d9c2ea8
=== How to use this, how to get the raw stack trace, and more: fburl.com/ASAN ===
W0812 19:22:04.903192 2396422 HandlerContext-inl.h:177] readEOF reached end of pipeline
READ of size 8 at 0x611000000568 thread T0
     #2 wangle/channel/Pipeline-inl.h:72         wangle::PipelineBase& wangle::PipelineBase::removeHelper<...>(wangle::ClientDispatcherBase<...>*, bool)
     #3 wangle/channel/Pipeline-inl.h:97         wangle::PipelineBase& wangle::PipelineBase::remove<...>(wangle::ClientDispatcherBase<...>*)
     #4 wangle/service/ClientDispatcher.h:27     wangle::ClientDispatcherBase<...>::~ClientDispatcherBase()
     #5 wangle/service/ClientDispatcher.h:63     wangle::SerialClientDispatcher<...>::~SerialClientDispatcher()
     #6 wangle/service/ServiceTest.cpp:89        wangle::ClientServiceFactory<...>::ClientService::~ClientService()
    #13 folly/Traits.h:279                       std::shared_ptr<...>::~shared_ptr()
    #14 wangle/service/ServiceTest.cpp:135       wangle::Wangle_ClientServerTest_Test::TestBody()
    #25 common/gtest/LightMain.cpp:9             main

0x611000000568 is located 40 bytes inside of 200-byte region [0x611000000540,0x611000000608)
freed by thread T0 here:
     #0 ServiceTest+0x59d790                     operator delete(void*)
     #1 wangle/channel/Pipeline-inl.h:26         wangle::Pipeline<...>::~Pipeline()
     #6 folly/Traits.h:279                       std::shared_ptr<...>::~shared_ptr()
     #7 wangle/bootstrap/BaseClientBootstrap.h:31 wangle::BaseClientBootstrap<...>::~BaseClientBootstrap()
     #8 wangle/bootstrap/ClientBootstrap.h:100   wangle::ClientBootstrap<...>::~ClientBootstrap()
    #16 wangle/service/ServiceTest.cpp:134       wangle::Wangle_ClientServerTest_Test::TestBody()
    #27 common/gtest/LightMain.cpp:9             main

previously allocated by thread T0 here:
     #0 ServiceTest+0x59d150                     operator new(unsigned long)
     #1 wangle/channel/Pipeline.h:167            wangle::Pipeline<...>::create()
     #2 wangle/service/ServiceTest.cpp:77        wangle::ClientPipelineFactory<...>::newPipeline(std::shared_ptr<...>)
     #3 wangle/bootstrap/BaseClientBootstrap.h:59 wangle::BaseClientBootstrap<...>::makePipeline(std::shared_ptr<...>)
     #4 wangle/bootstrap/ClientBootstrap.h:94    wangle::ClientBootstrap<...>::connect(folly::SocketAddress const&, std::chrono::duration<...>)::{lambda()#1}::operator()() const
     #5 folly/Function.h:290                     void folly::detail::function::FunctionTraits<...>::callSmall<...>(folly::detail::function::Data&)
     #6 folly/async/EventBase.cpp:629            folly::detail::function::FunctionTraits<...>::operator()()
     #8 wangle/bootstrap/ClientBootstrap.h:76    wangle::ClientBootstrap<...>::connect(folly::SocketAddress const&, std::chrono::duration<...>)
     #9 wangle/service/ServiceTest.cpp:123       wangle::Wangle_ClientServerTest_Test::TestBody()
    #20 common/gtest/LightMain.cpp:9             main

: AddressSanitizer: heap-use-after-free third-party-buck/gcc-4.9-glibc-2.20-fb/build/libgcc/include/c++/trunk/bits/stl_vector.h:267 in std::vector<std::shared_ptr<wangle::PipelineContext>, std::allocator<std::shared_ptr<wangle::PipelineContext> > >::_M_is_valid() const
Shadow bytes around the buggy address:
  0x0c227fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff8060: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff8070: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff8080: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff8090: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c227fff80a0: fa fa fa fa fa fa fa fa fd fd fd fd fd[fd]fd fd
  0x0c227fff80b0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c227fff80c0: fd fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff80d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c227fff80e0: 00 00 00 00 00 00 00 00 00 fa fa fa fa fa fa fa
  0x0c227fff80f0: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Heap right redzone:      fb
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack partial redzone:   f4
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==2396362==ABORTING
      ✓ wangle/service:ServiceTest - main 0.000s (PASS)
Summary (total time 1.91s):
  PASS: 9
  FAIL: 0
  SKIP: 0
  FATAL: 1
    wangle/service:ServiceTest - Wangle.ClientServerTest
  TIMEOUT: 0
  OMIT: 0
```

Differential Revision: D3714069

fbshipit-source-id: 178f11795a12742c5b2eee5179375c250758daba

wangle/service/ServiceTest.cpp

@@ -131,7 +131,6 @@ TEST(Wangle, ClientServerTest) {
   });
   EventBaseManager::get()->getEventBase()->loopForever();
   server.stop();
-  client.reset();
 }
 
 class AppendFilter : public ServiceFilter<std::string, std::string> {