Exclude all system-related CFs from CFS.allUserDefined()
Patch by Jason Brown, reviewed by brandonwilliams for CASSANDRA-5160
Merge branch 'cassandra-1.2' into trunk
Don't remove tokens for node we know in System.peers

patch by slebresne; reviewed by driftx for CASSANDRA-5121
Merge branch 'cassandra-1.2' into trunk