index: use `index.get_rev` in `exchange._pullapplyphases`

Differential Revision: https://phab.mercurial-scm.org/D7347

mercurial/exchange.py

@@ -2101,7 +2101,7 b' def _pullapplyphases(pullop, remotephase'
         dheads = []
     unfi = pullop.repo.unfiltered()
     phase = unfi._phasecache.phase
-    rev = unfi.changelog.nodemap.get
+    rev = unfi.changelog.index.get_rev
     public = phases.public
     draft = phases.draft