Removed an error check from debug mode that gets executed

n**2 times in closeTransaction where n is number of signals
sent in transaction. n can easily become 250.000 in a large
transaction.

ndb/src/ndbapi/Ndblist.cpp

@@ -592,13 +592,14 @@ Ndb::releaseSignal(NdbApiSignal* aSignal)
 #if defined VM_TRACE
   // Check that signal is not null
   assert(aSignal != NULL);
-
+#if 0
   // Check that signal is not already in list
   NdbApiSignal* tmp = theSignalIdleList;
   while (tmp != NULL){
     assert(tmp != aSignal);
     tmp = tmp->next();
   }
+#endif
 #endif
   creleaseSignals++;
   aSignal->next(theSignalIdleList);