Set keepalive on MessagingService connections
patch by Jianwei Zhang; reviewed by jbellis for CASSANDRA-7170
Merge branch 'cassandra-1.2' into cassandra-2.0
remove duplicate queries for local tokens

patch by dbrosius reviewed by ayeschenko for cassandra-7182
Merge branch 'cassandra-1.2' into cassandra-2.0
Merge branch 'cassandra-2.0' into cassandra-2.1