Reuse mq connection when established instead of creating new connections

[zoperado]

Detailed Description

A clear and concise description of what the bug is. When app.java creates listener twice then mq fails to initialize the second listener https://github.com/hashgraph/hedera-hcs-sxc/blob/d2dd8ec94e10213b59f52cb8bcabadd6476c6b55/hcs-lib/src/main/java/com/hedera/hcslib/callback/OnHCSMessageCallback.java#L35

Actual Behavior Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'

Expected Behavior

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.

[gregscullard]

Maybe the connection to MQ should be established when the lib is first instantiated (in the constructor) rather than every time the app subscribes to a topic.