In ReplicationRecoveryImpl::_truncateOplogTo we lock the oplog's database and collection; however, we have a general principle that we can read from the oplog with a global IS lock, write to it without locking the database and collection.

For example the oplog cap maintainer thread only takes the global IX lock to truncate old entries in OplogCapMaintainerThread::_deleteExcessDocuments.

Let's change ReplicationRecoveryImpl to take the global X or IX lock (I'm not sure which) instead of locking the oplog's db and collection.