Clients need to shutdown

[saturnism]

Describe the bug
For Pub/Sub emulator, sometimes I get:

i.g.i.ManagedChannelOrphanWrapper        : *~*~*~ Channel ManagedChannelImpl{logId=1, target=dns:///localhost:32873} was not shutdown properly!!! ~*~*~*
    Make sure to call shutdown()/shutdownNow() and wait until awaitTermination() returns true.

Checking into the code, I'm not sure if we shutdown the clients gracefully, and thus shutdown all the managed channels. Shutdown can be done automatically if our beans implements AutoCloseable, or use @Bean(destroyMethod=...).

[elefeint]

@ddixit14 See if you can reproduce this issue in the new repo (on version 2.0.4)

[ddixit14]

Hi, I am not able to reproduce this issue in the new repo. You can probably have a look at this client library issue that may be related: googleapis/google-cloud-java#3648

[elefeint]

I've seen some Spring Integration output related to this, but nothing reproducible. So it's a race condition between spring context shutdown and the client library awaitTermination. Ultimately likely has to get fixed in the client library.