lfs: access revlog directly LFS is monkeypatching filelog.filelog and is then accessing various filelog attributes in the monkeypatched function. This is all fine. But some of the attributes being accessed by LFS are revlog centric and shouldn't be exposed on the file storage interface. This commit changes the monkeypatched functions to access proxied attributes on self._revlog instead of self. This should be safe to do because non-revlog repositories should not be using filelog instances: instead they should have a separate class to represent file storage. So it is reasonable for LFS to assume the _revlog attribute exists and points to a revlog. Differential Revision: https://phab.mercurial-scm.org/D4714