semi-ninja trivial IOE cleanup

patch by Aleksey Yeschenko; reviewed by Brandon Williams
Merge branch 'cassandra-1.2' into trunk

Conflicts:
	src/java/org/apache/cassandra/cql/QueryProcessor.java
	src/java/org/apache/cassandra/cql3/statements/ModificationStatement.java
	src/java/org/apache/cassandra/db/RetriedSliceFromReadCommand.java
	src/java/org/apache/cassandra/service/ReadCallback.java
	src/java/org/apache/cassandra/service/RowDataResolver.java