Merge pull request #16734 from wallyworld/racefix-fix

#16734

#16732 fixed a race failure but there was a small mistake in calling unlock.

## QA steps

run unit tests

core/cache/resident.go

@@ -230,6 +230,7 @@ func (r *Resident) CacheId() uint64 {
 func (r *Resident) registerWorker(w worker.Worker) func() {
  id := r.nextResourceId()
  r.mu.Lock()
+ defer r.mu.Unlock()
  // If this resident is already being evicted
  // don't register any new workers.
  if r.evicting {
@@ -242,7 +243,6 @@ func (r *Resident) registerWorker(w worker.Worker) func() {
  }
  }
  r.workers[id] = w
- r.mu.Unlock()
  return func() { r.deregisterWorker(id) }
 }