detect/loader: add threading coverity warning

detect/loader: add threading coverity warning

 lock_acquire: Calling pthread_mutex_lock acquires lock ThreadVars_.ctrl_mutex.
725        SCCtrlMutexLock(th_v->ctrl_mutex);

CID 1554214: (#1 of 1): Indefinite wait (BAD_CHECK_OF_WAIT_COND)
dead_wait: A wait is performed without ensuring that the condition is not already satisfied while holding lock ThreadVars_.ctrl_mutex. This can cause a deadlock if the notification happens before the lock is acquired.
      Acquire the lock, then check the wait condition in a loop, without releasing with the lock before the wait. This will prevent deadlocks and failed conditions from spurious wakeups.