Fix Debian bug
#494889 (fetching from static-
http://... broken)
Changeset
6605a03cbf87 which fixed issue965 (hg clone static-http
does not work for empty repos) broke cloning of repos with old layout
(without store) via static-http.
This fix makes cloning from old-style repositories possible again,
but will not allow cloning of empty old-style repositories as this
can not be detected reliably.