lightningd: free peer->uc when openingd fails.

This avoids reuse which can cause confusion; the long-term fix is to
rewrite this to use real channels like dualfunding does.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/opening_control.c

@@ -574,6 +574,8 @@ static void openingd_failed(struct subd *openingd, const u8 *msg,
 
 	/* Noop if we're not funder. */
 	opening_funder_failed_cancel_commands(uc, desc);
+	/* Detaches from ->peer */
+	tal_free(uc);
 }
 
 struct openchannel_hook_payload {