cleanup and add new test

Author: SergioBenitez

core/lib/tests/drop-in-async-context.rs

@@ -62,8 +62,6 @@ mod main {
 
     #[test]
     fn test_execute_directly() {
-        rocket::execute(async {
-            rocket::execute(super::rocket().launch()).unwrap();
-        });
+        rocket::execute(super::rocket().launch()).unwrap();
     }
 }