[#1700] gc: Take mode mutex in locks handlers

Change-Id: I4408eae3aed936f85427b6246dcf727bd6813a0d
Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/local_object_storage/shard/gc.go

@@ -664,7 +664,10 @@ func (s *Shard) HandleExpiredTombstones(ctx context.Context, tss []meta.Tombston
 // HandleExpiredLocks unlocks all objects which were locked by lockers.
 // If successful, marks lockers themselves as garbage.
 func (s *Shard) HandleExpiredLocks(ctx context.Context, epoch uint64, lockers []oid.Address) {
-	if s.GetMode().NoMetabase() {
+	s.m.RLock()
+	defer s.m.RUnlock()
+
+	if s.info.Mode.NoMetabase() {
 		return
 	}
 
@@ -727,7 +730,10 @@ func (s *Shard) inhumeUnlockedIfExpired(ctx context.Context, epoch uint64, unloc
 
 // HandleDeletedLocks unlocks all objects which were locked by lockers.
 func (s *Shard) HandleDeletedLocks(ctx context.Context, lockers []oid.Address) {
-	if s.GetMode().NoMetabase() {
+	s.m.RLock()
+	defer s.m.RUnlock()
+
+	if s.info.Mode.NoMetabase() {
 		return
 	}