SERVER-15062 test prepareFreezeResponse in the TopologyCoordinator
SERVER-15052 make prepareFreshResponse return an error when the callback is canceled in the TopologyCoordinator
SERVER-15062 test commands fail when their callback is canceled in the TopologyCoordinator
SERVER-15113 fix order of cancellation vs. signaling in elect_cmd_runner
SERVER-14023 Add RHEL 7 Enterprise .rpm
SERVER-13243 Add Ubuntu 14.04 Enterprise .deb
SERVER-5022 allow covered queries with shard filter
SERVER-15114 Remove misleading init script comment
SERVER-14561 Implement heartbeat scheduling and reconfig logic in TopologyCoordinator.
SERVER-15118 Clarify locking rules in ReplicationCoordinatorImpl.

Notably, _rsConfig, _rsConfigState and _thisMembersConfigIndex have a locking mode
that makes them safe to read in executor context without holding _mutex.
SERVER-15075 Check return value of ReplicaSetTagMatch::update when waiting for write concern
Merge with upstream/master.