Fix SecondaryIndexManager#deleteFromIndexes()

patch by Sergio Bossa; reviewed by Sam Tunnicliffe for CASSANDRA-6711
Merge branch 'cassandra-1.2' into cassandra-2.0
Merge branch 'cassandra-2.0' into trunk

Conflicts:
	src/java/org/apache/cassandra/db/index/SecondaryIndexManager.java
Fix bad merge