Exit with 1 if the connection to the XMPP server fails

This helps the system understand if the process started correctly or not,
when systemd is not used

fix #3078

src/main.cpp

@@ -203,6 +203,8 @@ int main(int ac, char** av)
 #ifdef CARES_FOUND
   DNSHandler::instance.destroy();
 #endif
+  if (!xmpp_component->ever_auth)
+    return 1; // To signal that the process did not properly start
   log_info("All connections cleanly closed, have a nice day.");
   return 0;
 }