fix #1226 cleanup index.lock

The issue is in VfsScm code path - we missed to clean the index.lock after lock acquired.   The reason is pretty subtle.  The deployment lock is historically relying on IRepositoryFactory being ninjected.   However, LiveScmEditorController ninjects IRepository (not IRepositoryFactory) leading to the issue.  I believe this is a standalone case.
No, it does not relate to issue.  However, the benefit is it handles read-only file  (See DeleteFileSystemInfo).