Check all INTERNAL_IP states for seed match.

Patch by Brandon Williams, reviewed by Jason Brown for CASSANDRA-6523
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/gms/Gossiper.java
Merge branch 'cassandra-2.0' into cassandra-2.1