Fix spin loop in AtomicSortedColumns

patch by graham sanderson and benedict; reviewed by yukim for
CASSANDRA-7546
Merge branch 'cassandra-2.1' into trunk
Fix handling of EXECUTE with skip_metadata=false

patch by Aleksey Yeschenko and Jake Luciani; reviewed by Sylvain
Lebresne
Merge branch 'cassandra-2.1' into trunk
Update java driver to 2.1.2

patch by snazy; reviewed by slebresne for CASSANDRA-7692