vfs: use 'vfs' module directly in 'mercurial.statichttprepo'

Now that the 'vfs' classes moved in their own module, lets use the new module
directly. We update code iteratively to help with possible bisect needs in the
future.

mercurial/statichttprepo.py

@@ -24,6 +24,7 b' from . import ('
     store,
     url,
     util,
+    vfs as vfsmod,
 )
 
 urlerr = util.urlerr
@@ -86,7 +87,7 b' def build_opener(ui, authinfo):'
     urlopener = url.opener(ui, authinfo)
     urlopener.add_handler(byterange.HTTPRangeHandler())
 
-    class statichttpvfs(scmutil.abstractvfs):
+    class statichttpvfs(vfsmod.abstractvfs):
         def __init__(self, base):
             self.base = base