SERVER-12641 support projections on DBRef fields
SERVER-11982 connection error when doing sharded cluster upgrade following recommended procedure
SERVER-11982 connection error when doing sharded cluster upgrade following recommended procedure

Make connPoolSync clear all global connection pools
SERVER-12554 There's no need to iterate all over the runner if limit
is set, because this is really expensive (the scan it done under
lock scope).
SERVER-12554 Mimic 2.4 behaviour and lazily yield in order to
avoid a regression whne scanning a small set of documents.
Merge remote-tracking branch 'upstream/master'