fix CME in SessionInfo updateProgress affecting netstats
patch by Josh McKenzie; reviewed by Tyler Hobbs for CASSANDRA-6577
Merge branch 'cassandra-2.0' into cassandra-2.1
Merge branch 'cassandra-2.1' into trunk
Fix overflow of memtable_total_space_in_mb
patch by Benedict Elliott Smith; reviewed by jbellis for CASSANDRA-6753
Merge branch 'cassandra-2.1' into trunk