windows: use abspath in subrepo

We replace `os.path.abspath` with `util.abspath`. This should solve more "drive
capitalization" issue on Windows.

Differential Revision: https://phab.mercurial-scm.org/D11065

mercurial/subrepo.py

@@ -60,7 +60,7 b' def _expandedabspath(path):'
     expandedpath = urlutil.urllocalpath(util.expandpath(path))
     u = urlutil.url(expandedpath)
     if not u.scheme:
-        path = util.normpath(os.path.abspath(u.path))
+        path = util.normpath(util.abspath(u.path))
     return path