ReplicationCoordinatorImpl::signalDrainComplete takes the RSTL lock in X mode first before acquiring the FCV lock for reconfig. Based on
SERVER-33043, the FCV lock should be acquired before the global lock. I think this implies that the FCV lock should also be acquired before the RSTL lock. Because operation like this would take the FCV lock first before getting the global / RSTL locks. FixedFCVRegion has an invariant to check for that the global lock is not being held first. I think we should extend the invariant to check for RSTL lock as well.