shelve: directly use repo.vfs.join

The 'repo.join' method is about to be deprecated.

hgext/shelve.py

@@ -79,8 +79,8 b' class shelvedfile(object):'
     def __init__(self, repo, name, filetype=None):
         self.repo = repo
         self.name = name
-        self.vfs = vfsmod.vfs(repo.join(shelvedir))
-        self.backupvfs = vfsmod.vfs(repo.join(backupdir))
+        self.vfs = vfsmod.vfs(repo.vfs.join(shelvedir))
+        self.backupvfs = vfsmod.vfs(repo.vfs.join(backupdir))
         self.ui = self.repo.ui
         if filetype:
             self.fname = name + '.' + filetype
@@ -221,7 +221,7 b' class shelvedstate(object):'
         repo.vfs.unlinkpath(cls._filename, ignoremissing=True)
 
 def cleanupoldbackups(repo):
-    vfs = vfsmod.vfs(repo.join(backupdir))
+    vfs = vfsmod.vfs(repo.vfs.join(backupdir))
     maxbackups = repo.ui.configint('shelve', 'maxbackups', 10)
     hgfiles = [f for f in vfs.listdir()
                if f.endswith('.' + patchextension)]