Patched version of Disruptor Thrift Server

patch by Mikhail Stepura; reviewed by Brandon Williams for CASSANDRA-6545
Cleanup selector's keys.

patch by Mikhail Stepura; reviewed by Brandon Williams for CASSANDRA-6546
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	src/java/org/apache/cassandra/thrift/CustomTHsHaServer.java
Merge branch 'cassandra-2.0' into cassandra-2.1