SERVER-14058 Fix deadlock in ReplicationExecutor::shutdown().

Joining the network worker thread pool cannot be done while holding the
ReplicationExecutor's _mutex, because a thread in the pool might need that
_mutex to finish its work.
SERVER-14144 Aggregation cursor error shouldn't swallow Runner error
SERVER-9710 remove _nosleep check for balancer
Merge remote-tracking branch 'upstream/master'