grpc throws exceptions after sending message, even if message succeeds

[zoperado]

Detailed Description A clear and concise description of what the bug is. grpc throws exceptions after sending message,

SEVERE: *~*~*~ Channel ManagedChannelImpl{logId=1, target=hcs.testnet.mirrornode.hedera.com:5600} was not shutdown properly!!! ~*~*~*
    Make sure to call shutdown()/shutdownNow() and wait until awaitTermination() returns true.
java.lang.RuntimeException: ManagedChannel allocation site
	at io.grpc.internal.ManagedChannelOrphanWrapper$ManagedChannelReference.<init>(ManagedChannelOrphanWrapper.java:94)
	at io.grpc.internal.ManagedChannelOrphanWrapper.<init>(ManagedChannelOrphanWrapper.java:52)
	at io.grpc.internal.ManagedChannelOrphanWrapper.<init>(ManagedChannelOrphanWrapper.java:43)
	at io.grpc.internal.AbstractManagedChannelImplBuilder.build(AbstractManagedChannelImplBuilder.java:512)
	at com.hedera.hashgraph.sdk.mirror.MirrorClient.<init>(MirrorClient.java:17)
	at com.hedera.hcs.sxc.plugin.mirror.subscribe.MirrorTopicSubscriber.subscribe(MirrorTopicSubscriber.java:82)
	at com.hedera.hcs.sxc.plugin.mirror.subscribe.MirrorTopicSubscriber.run(MirrorTopicSubscriber.java:74)
	at java.base/java.lang.Thread.run(Thread.java:844)

Actual Behavior To reproduce create an OutboundHCSMessage and send any message. Expected Behavior No grpc stack traces on stdout on successful messages.

Environment:

• Java: [e.g. OpenJDK 11.0.4]
• Node: [e.g. v12.9.1-x86]
• OS: [e.g. Ubuntu 18.04]
• Version: [e.g. 1.0.1]

Additional Context Add any other context about the problem here. Attach any logs here, if applicable.