SERVER-15900: secondaries should stripe writes by doc if doc locking is on
SERVER-13635: add isDurable to StorageEngine and use for GLE
SERVER-15819: fix privilege check on currentOpCtx
SERVER-15870 Prune command stats for commands that haven't run

Signed-off-by: Dan Pasette <dan@mongodb.com>
Merge remote-tracking branch 'upstream/master'