!68 add inner default runtime when neither `--runtime` nor `default-runtime` is specified

Merge pull request !68 from gaohuatao/next_llt

src/config/isulad_config.h

@@ -25,6 +25,7 @@ extern "C" {
 #endif
 
 #define DEFAULT_IM_SERVER_SOCK_ADDR "unix:///var/run/isulad/isula_image.sock"
+#define DEFAULT_RUNTIME_NAME "lcr"
 
 struct isulad_conf {
     pthread_rwlock_t isulad_conf_rwlock;

src/services/execution/execute/execution_create.c

@@ -729,9 +729,9 @@ static int preparate_runtime_environment(const container_create_request *request
     } else {
         *runtime = conf_get_default_runtime();
     }
+
     if (*runtime == NULL) {
-        *cc = ISULAD_ERR_INPUT;
-        return -1;
+        *runtime = util_strdup_s(DEFAULT_RUNTIME_NAME);
     }
 
     if (runtime_check(*runtime, &runtime_res) != 0) {