tracer: fix trace_stop removal from list

Fix the way we detect the previous element when removing from list
Before this change, if there were multiple elements in the list, they
were leaking due to the bad handling of the list removal.

(cherry picked from commit dae9817)

modules/tracer/tracer.c

@@ -2837,7 +2837,7 @@ static mi_response_t *sip_trace_mi_stop(const mi_params_t *params,
 	hash=it->hash;
 
 	/* search for the previous element */
-	for (prev=NULL, it=(*dyn_trace_list); it && it->next; it = it->next) {
+	for (prev=NULL, it=(*dyn_trace_list); it && it->hash != hash && it->next; it = it->next) {
 		if (it->next->hash == hash)
 			break;
 		else