Fixes a destruction problem in GridConnectHub that could cause the write thread to deadlock at exit time. This caused leakage of threads.
Fixes a destruction problem in GridConnectHub that could cause the write thread to deadlock at exit time. This caused leakage of threads.

bakerstu/openmrn,bakerstu/openmrn,bakerstu/openmrn,bakerstu/openmrn,bakerstu/openmrn,bakerstu/openmrn