Don't send confusing info on timeouts

patch by slebresne; reviewed by jbellis for CASSANDRA-6491
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/service/ReadCallback.java
	src/java/org/apache/cassandra/service/StorageProxy.java
Merge branch 'cassandra-2.0' into trunk