vmspawn-qmp: pass bridge to on_cont_complete via invoke userdata

The callback already has the bridge available — but it was reaching for
it via qmp_client_get_userdata() instead of through its own userdata
parameter. Pass the bridge directly from vmspawn_qmp_start() so the
callback can read its argument the way the rest of the file does. No
behaviour change.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

src/vmspawn/vmspawn-qmp.c

@@ -1060,10 +1060,10 @@ static int on_cont_complete(
                 int error,
                 void *userdata) {
 
-        VmspawnQmpBridge *bridge = ASSERT_PTR(qmp_client_get_userdata(client));
-
         assert(client);
 
+        VmspawnQmpBridge *bridge = ASSERT_PTR(userdata);
+
         if (error < 0) {
                 log_error_errno(error, "Failed to resume QEMU execution: %s", strna(error_desc));
                 return sd_event_exit(qmp_client_get_event(client), error);
@@ -1077,5 +1077,5 @@ static int on_cont_complete(
 int vmspawn_qmp_start(VmspawnQmpBridge *bridge) {
         assert(bridge);
 
-        return qmp_client_invoke(bridge->qmp, /* ret_slot= */ NULL, "cont", /* args= */ NULL, on_cont_complete, /* userdata= */ NULL);
+        return qmp_client_invoke(bridge->qmp, /* ret_slot= */ NULL, "cont", /* args= */ NULL, on_cont_complete, bridge);
 }