Fix test #620: no double launch, weave stop instead of kill -9.

- Now that router and proxy have been merged, we should only call `weave launch` once.
- `sudo kill -9` was introduced because we previously had `docker kill` (see: http://github.com/weaveworks/weave/commit/cb73b738621d57727072ae998cdeaec337f23a1a), because we had no `weave stop-proxy` yet (see: http://github.com/weaveworks/weave/commit/e31f21a6d224d61de1d8a940ea4b0b45cebc9723). Pre-proxy-merge, this should just have been `weave stop-proxy`, and now that router and proxy have been merged, we should just call `weave stop`.

test/620_proxy_entrypoint_command_test.sh

@@ -26,13 +26,8 @@ run_container "grep ^1$ /sys/class/net/ethwe/carrier"
 build_image false '["/bin/false"]' ''
 run_container "--entrypoint='grep' false ^1$ /sys/class/net/ethwe/carrier"
 
+weave_on $HOST1 stop
 weave_on $HOST1 launch --ipalloc-range 10.2.2.0/24
-# NOTE: docker-kill hangs (https://github.com/docker/docker/issues/31447), so we
-# kill directly the weaveproxy process instead.
-WEAVEPROXY_PID=$(container_pid $HOST1 weaveproxy)
-$SSH $HOST1 "ps aux | grep weaveproxy"
-run_on $HOST1 "sudo kill -9 $WEAVEPROXY_PID"
-weave_on $HOST1 launch
 
 assert_raises "proxy docker_on $HOST1 run check-ethwe-up"