Remove Internal Phoenix Connections from parent LinkedQueue when closed

In https://issues.apache.org/jira/browse/PHOENIX-5872

We started maintaining parent-child relationships between phoenix connections to close those connections. But after closing those child connections we should be removing them from the Queue which is being maintained for the same.

Here:

https://github.com/apache/phoenix/blob/affa9e889efcc2ad7dac009a0d294b09447d281e/phoenix-core/src/main/java/org/apache/phoenix/compile/MutatingParallelIteratorFactory.java#L114

If not removed from the queue, and if the parent connection is being reused: we are observing the OOM issue on the container side during the mapper run.