mq: use an unfiltered property cache for the queue object

The same `queue` object should be used in all situations. This allows to store
global states on the object (like the reworked shelve extension plans to).  The
queue object does not need to be distinct for all possible views (no reference
to the repo/view used at creation time) it's even a bit surprising that mq still
works with the current code.

hgext/mq.py

@@ -65,6 +65,7 b' from mercurial.lock import release'
 from mercurial import commands, cmdutil, hg, scmutil, util, revset
 from mercurial import repair, extensions, error, phases
 from mercurial import patch as patchmod
+from mercurial import localrepo
 import os, re, errno, shutil
 
 commands.norepo += " qclone"
@@ -3410,7 +3411,7 b' def mqphasedefaults(repo, roots):'
 
 def reposetup(ui, repo):
     class mqrepo(repo.__class__):
-        @util.propertycache
+        @localrepo.unfilteredpropertycache
         def mq(self):
             return queue(self.ui, self.baseui, self.path)