agent: skip test_load_kernel_module if non-root

We need root privilege to load a real kernel module.

Fixes: #4704
Signed-off-by: Peng Tao <bergwolf@hyper.sh>

src/agent/src/rpc.rs

@@ -2058,6 +2058,7 @@ mod tests {
         let result = load_kernel_module(&m);
         assert!(result.is_err(), "load module should failed");
 
+        skip_if_not_root!();
         // case 3: normal module.
         // normally this module should eixsts...
         m.name = "bridge".to_string();