treemanifest: fix a "treeinmem" case

f2c5b9d48b29 (manifest: make treemanifestctx store the repo,
2016-10-18) broke most tests when run with treeinmem=True. The
treeinmem mode can not be enabled by the user, so this did not break
anything in practice, but it's useful to have it working for testing
the treemanifest code.

mercurial/manifest.py

@@ -1427,7 +1427,7 b' class treemanifestctx(object):'
                 m.setnode(self._node)
                 self._data = m
             else:
-                text = revlog.revision(self._node)
+                text = rl.revision(self._node)
                 arraytext = array.array('c', text)
                 rl.fulltextcache[self._node] = arraytext
                 self._data = treemanifest(dir=self._dir, text=text)