Revert "Add locking to concurrently-update bool"

This reverts commit a9598fb.

go/vt/vttablet/tabletmanager/rpc_replication.go

@@ -726,25 +726,12 @@ func (tm *TabletManager) setReplicationSourceSemiSyncNoAction(ctx context.Contex
 	return tm.setReplicationSourceLocked(ctx, parentAlias, timeCreatedNS, waitPosition, forceStartReplication, SemiSyncActionNone)
 }
 
-// isSetReplicationSourceLockedRunning returns true if setReplicationSourceLocked is running.
-// A mutex is needed because _isSetReplicationSourceLockedRunning is accessed concurrently.
-func (tm *TabletManager) isSetReplicationSourceLockedRunning() bool {
-	tm.mutex.Lock()
-	defer tm.mutex.Unlock()
-	return tm._isSetReplicationSourceLockedRunning
-}
-
-// setReplicationSourceLockedRunning sets _isSetReplicationSourceLockedRunning under a lock.
-// A mutex is needed because _isSetReplicationSourceLockedRunning is accessed concurrently.
-func (tm *TabletManager) setReplicationSourceLockedRunning(running bool) {
-	tm.mutex.Lock()
-	defer tm.mutex.Unlock()
-	tm._isSetReplicationSourceLockedRunning = running
-}
-
 func (tm *TabletManager) setReplicationSourceLocked(ctx context.Context, parentAlias *topodatapb.TabletAlias, timeCreatedNS int64, waitPosition string, forceStartReplication bool, semiSync SemiSyncAction) (err error) {
-	tm.setReplicationSourceLockedRunning(true)
-	defer tm.setReplicationSourceLockedRunning(false)
+	tm._isSetReplicationSourceLockedRunning = true
+
+	defer func() {
+		tm._isSetReplicationSourceLockedRunning = false
+	}()
 
 	// End orchestrator maintenance at the end of fixing replication.
 	// This is a best effort operation, so it should happen in a goroutine
@@ -1142,7 +1129,7 @@ func (tm *TabletManager) handleRelayLogError(err error) error {
 // repairReplication tries to connect this server to whoever is
 // the current primary of the shard, and start replicating.
 func (tm *TabletManager) repairReplication(ctx context.Context) error {
-	if tm.isSetReplicationSourceLockedRunning() {
+	if tm._isSetReplicationSourceLockedRunning {
 		// we are actively setting replication source,
 		// repairReplication will block due to higher
 		// authority holding a shard lock (PRS on vtctld)