Fix thundering herd on endpoint cache invalidation
patch by rbranson and jbellis for CASSANDRA-6345
merge from 1.2
Merge branch 'cassandra-2.0' into trunk
fix build
Merge branch 'cassandra-1.2' into cassandra-2.0
Merge branch 'cassandra-2.0' into trunk
fix build more
Merge branch 'cassandra-1.2' into cassandra-2.0
Merge branch 'cassandra-2.0' into trunk
fix merge
Merge branch 'cassandra-2.0' into trunk