qemu-ga: don't warn on no command return

This is a valid condition when a command chooses to not emit a
success response.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

qemu-ga.c

@@ -488,8 +488,6 @@ static void process_command(GAState *s, QDict *req)
             g_warning("error sending response: %s", strerror(ret));
         }
         qobject_decref(rsp);
-    } else {
-        g_warning("error getting response");
     }
 }