action-scripts: check a return code of get_service_fd

>>>     CID 190177:  Integer handling issues  (NEGATIVE_RETURNS)
>>>     rpc_sk is passed to a parameter that cannot be negative.
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/action-scripts.c

@@ -108,6 +108,8 @@ int rpc_send_fd(enum script_actions act, int fd)
 		return -1;
 
 	rpc_sk = get_service_fd(RPC_SK_OFF);
+	if (rpc_sk < 0)
+		return -1;
 
 	pr_debug("\tRPC\n");
 	return send_criu_rpc_script(act, (char *)action, rpc_sk, fd);
@@ -128,6 +130,10 @@ int run_scripts(enum script_actions act)
 
 		pr_debug("\tRPC\n");
 		rpc_sk = get_service_fd(RPC_SK_OFF);
+		if (rpc_sk < 0) {
+			ret = -1;
+			goto out;
+		}
 		ret = send_criu_rpc_script(act, (char *)action, rpc_sk, -1);
 		goto out;
 	}