xwayland: Give up on EI on setup failure

If we fail to setup EI, give up on using EI for XTEST and restore the
default XTEST handlers.

This happens when neither the portal nor the socket backends are usable.

This does not affect the portal operation though, if the user choose not
to allow a particular client, Xwayland would continue to use EI.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Joshua Ashton <joshua@froggi.es>
(cherry picked from commit 6b56ae68e5)

hw/xwayland/xwayland-xtest.c

@@ -387,6 +387,8 @@ setup_ei(ClientPtr client)
         xwl_ei_client = NULL;
         ei_unref(ei);
         error_ei("EI setup failed\n");
+        /* We failed to setup EI using either backends, give up on EI. */
+        xwayland_restore_xtest();
     }
 
  out: