Memory leak when STABLE.send_stable_msg_to_coord_only=true

Running MPerf with conf/fast-local.xml (2 members on the same host, 20 million messages each) creates a memory leak in 3.4.x.

This runs perfectly 3.2.8.Final, so it must be something that was introduced in 3.3.x (3.4.x at this time has almost no diffs to 3.3.0.Final).