RepairTask didn't send a correct message on IllegalArgumentException

patch by Mikhail Stepura; reviewed by Yuki Morishita for CASSANDRA-7336
Merge branch 'cassandra-1.2' into cassandra-2.0

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