windows: use abspath in hgwebdir

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

Differential Revision: https://phab.mercurial-scm.org/D11064

mercurial/hgweb/hgwebdir_mod.py

@@ -70,7 +70,7 b' def findrepos(paths):'
         except KeyError:
             repos.append((prefix, root))
             continue
-        roothead = os.path.normpath(os.path.abspath(roothead))
+        roothead = os.path.normpath(util.abspath(roothead))
         paths = scmutil.walkrepos(roothead, followsym=True, recurse=recurse)
         repos.extend(urlrepos(prefix, roothead, paths))
     return repos