workingctx: duplicate status list received at _poststatus hook

basectx.status may reorder the list after workingctx._poststatus is called,
so workingctx must copy it.  Otherwise, wctx.deleted() would return "unknown"
files, for example.

mercurial/context.py

@@ -1375,7 +1375,7 b' class workingctx(committablectx):'
         susposed to be linking to.
         """
         s[0] = self._filtersuspectsymlink(s[0])
-        self._status = s
+        self._status = s[:]
         return s
 
     def _dirstatestatus(self, match=None, ignored=False, clean=False,