dirstate: stop using `oldstate` in `dirstate._addpath`

We don't need to pass the oldstate around, so lets use the new property
instead.

Differential Revision: https://phab.mercurial-scm.org/D10965

mercurial/dirstate.py

@@ -451,7 +451,8 b' class dirstate(object):'
         possibly_dirty=False,
     ):
         oldstate = self[f]
-        if state == b'a' or oldstate == b'r':
+        entry = self._map.get(f)
+        if state == b'a' or entry is not None and entry.removed:
             scmutil.checkfilename(f)
             if self._map.hastrackeddir(f):
                 msg = _(b'directory %r already in dirstate')