controller: Properly notify waiting thread after INVALID_KE_PAYLOAD retry failed

When initiating a Child SA with a CREATE_CHILD_SA exchange, the initial
exchange could fail with an INVALID_KE_PAYLOAD notify.  The initiation
would then get retried from scratch (the `child_sa_t` object is destroyed
and a new one created).  If it fails again, the previous code didn't
signal the waiting thread.  If it did not set a timeout, it would wait
indefinitely.

Using a different `status_t` value avoids any confusion with NEED_MORE
that's used to indicate that the callback returned FALSE (e.g. if the
IKE_SA would go down before concluding the retry).

Fixes: c39b0c883d ("controller: Keep following initiate() if the first DH guess was wrong")

src/libcharon/control/controller.c

@@ -341,13 +341,12 @@ METHOD(listener_t, child_state_change, bool,
 					case CHILD_RETRYING:
 						/* retrying with a different DH group; survive another
 						 * initiation round */
-						this->status = NEED_MORE;
+						this->status = INVALID_ARG;
 						return TRUE;
 					case CHILD_CREATED:
-						if (this->status == NEED_MORE)
+						if (this->status == INVALID_ARG)
 						{
 							this->status = FAILED;
-							return TRUE;
 						}
 						break;
 					default: