agent-manager: cancel secrets requests on an error

It might be that the user didn't supply the secrets in time and the dbus call
timed out. The agent should now hide the secrets dialog and we must let it know.

https://bugzilla.redhat.com/show_bug.cgi?id=1272023
(cherry picked from commit 5d1cac81a0)

src/settings/nm-agent-manager.c

@@ -816,6 +816,9 @@ get_done_cb (NMSecretAgent *agent,
 			req_complete_error (parent, error);
 			g_error_free (error);
 		} else {
+			/* Tell the failed agent we're no longer interested. */
+			nm_secret_agent_cancel_secrets (parent->current, parent->current_call_id);
+
 			/* Try the next agent */
 			request_next_agent (parent);
 		}