mercurial.el: don't raise an error from find-file-hook find-file() shouldn't fail even if unreadable .hg directory is exists. Not enabling hg-mode is sufficient for that senario.

adding da/foo
adding foo
% manifest
200 Script output follows


drwxr-xr-x da
-rw-r--r-- 4 foo


200 Script output follows


-rw-r--r-- 4 foo