Allow unauthenticated set_keyspace() calls

patch by Aleksey Yeschenko; reviewed by Jonathan Ellis for
CASSANDRA-5423
Merge branch 'cassandra-1.2' into trunk
back up new sstables before creating a new View (which makes the new one eligible for compaction)

patch by jbellis, reviewed by marcuse for CASSANDRA-5410
Merge branch 'cassandra-1.2' into trunk