Update tests to adapt new type of fields in resource

The type has been changed to Option type.

Signed-off-by: Tim Zhang <tim@hyper.sh>

tests/builder.rs

@@ -159,7 +159,7 @@ pub fn test_blkio_res_build() {
     let h = Box::new(&*h);
     let cg: Cgroup = CgroupBuilder::new("test_blkio_res_build", h)
         .blkio()
-        .weight(Some(100))
+        .weight(100)
         .done()
         .build();