SERVER-15816 explained upserts against an empty collection shouldn't try to create a collection
SERVER-15627 Use LogComponent::kWrites where appropriate
SERVER-15380 Tune MONGO_LOG_DEFAULT_COMPONENT declarations
SERVER 14425: fix deadlock retry in write commands
Merge remote-tracking branch 'nextdoor/master'
SERVER-13962 fixed snappy-1.1.2 windows build
SERVER-13962 upgrade snappy from 1.03 to 1.1.2
SERVER-11103 test that fsyncLocked secondaries will still participate in elections
SERVER-15527 rename find command 'query' field to 'filter'
SERVER-15813 Add documentation to advanceTo() and customLocate().
SERVER-15768 Better propagate auth failures up the network interface.
SERVER-15768 Proactively dispose of dead connections in NetworkInterfaceImpl's connection pool.
SERVER-15527 auth test for new explain
Merge remote-tracking branch 'root/master'
SERVER-15833 Require basic compatibility between old and new configs for force reconfig.

Force reconfig is really about letting changing topology when the primary is not
available. It is not intended to allow you to make the cluster inconsistent by
marking non-index building nodes as index-building, or arbiters as non-arbiters,
e.g.
SERVER-15832 Prevent primary from stepping down while holding global lock.

Specifically, this prevents it from occuring during reconfig, either heartbeat
or command-initiated.
SERVER-15779 Clear drain mode flag when switching out of primary state.

Also, maintain the global lock held in multiApply while calling applyOpsToOplog.
Putting applyOpsToOplog outsite that critical section allows a race in which a
node might exit drain mode due to step-down and then be reelected primary, leading
to risky behavior.
SERVER 14425: fix deadlock retry in write commands
Merge remote-tracking branch 'nextdoor/master'
SERVER-15836 Clean up several rollback js tests.