fix more ScopeGuard.h includes
fix more ScopeGuard.h includes

Summary: Fix the places that are transitively including ScopeGuard.h through FBString.h

Reviewed By: knekritz

Differential Revision: D3806944

fbshipit-source-id: 2f91b948dc340b9f7d34d031f292b76ebc419687

peterlei/fboss,peterlei/fboss,peterlei/fboss,peterlei/fboss