Fix broken Vagrant build

[gkristic]

Although provisioning succeeds, the Vagrant box fails to build Vitess on first vagrant ssh. It aborts on a missing Java compiler when trying to build Zookeeper, thus missing plenty of dependencies:

BUILD FAILED
/vagrant/dist/vt-zookeeper-3.4.14/zookeeper-3.4.14/build.xml:321: Unable to find a javac compiler;
com.sun.tools.javac.Main is not on the classpath.
Perhaps JAVA_HOME does not point to the JDK.
It is currently set to "/usr/lib/jvm/java-8-openjdk-amd64/jre"

Total time: 1 minute 19 seconds
ERROR: Zookeeper build failed

Note the JAVA_HOME.

Furthermore, although bootstrap.sh aborts, build.sh still continues. This makes the process end with a misleading error on Go dependencies:

... <<< Plenty of packages omitted here for brevity >>> ...
go/cmd/zk/zkcmd.go:36:2: cannot find package "golang.org/x/crypto/ssh/terminal" in any of:
        /vagrant/src/vitess.io/vitess/vendor/golang.org/x/crypto/ssh/terminal (vendor tree)
        /usr/local/go/src/golang.org/x/crypto/ssh/terminal (from $GOROOT)
        /vagrant/src/golang.org/x/crypto/ssh/terminal (from $GOPATH)
go/vt/vtgate/vtgateservice/vtgateservice_testing/mock_vtgateservice.go:10:2: cannot find package "github.com/golang/mock/gomock" in any of:
        /vagrant/src/vitess.io/vitess/vendor/github.com/golang/mock/gomock (vendor tree)
        /usr/local/go/src/github.com/golang/mock/gomock (from $GOROOT)
        /vagrant/src/github.com/golang/mock/gomock (from $GOPATH)
Makefile:47: recipe for target 'build' failed
make: *** [build] Error 1
\Build completed

This PR changes openjdk-7-jdk to openjdk-8-jdk, that is now available for the Ubuntu version (see here), matching the version used for Docker. (An example for #4780.) It also makes the build script abort on errors, just like bootstrap.sh does. This seems to make #4883 obsolete.