another critical bug: GEODE-6522

[Bruce Schuchardt]

I'd like to get the fix for GEODE-6522 into the release.  This is a 
shutdown issue where a server can hang not realizing that the rest of 
the cluster has shut down.  This bug isn't in other releases of Geode.

https://issues.apache.org/jira/browse/GEODE-6522