confd: fix memory leak in handle_sr_shell_update()

Found by Coverity Scan, CID 331029

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/confd/src/ietf-system.c

@@ -800,6 +800,7 @@ static sr_error_t handle_sr_shell_update(augeas *aug, sr_session_ctx_t *sess, st
 		err = SR_ERR_OK;
 	}
 	free(shell);
+	free(user);
 
 	return err;
 }