perf: always pass node to revlog.revision()

I removed this in 73c3e226d2fc thinking it wasn't necessary. In fact,
we need to always pass a node so the code is compatible with revisions
before d7d64b89a65c.

The new code uses a variable to avoid check-style complaining
about "r.revision(r.node(" patterns.

contrib/perf.py

@@ -865,7 +865,9 b' def perfrevlog(ui, repo, file_=None, sta'
             dist = -1 * dist
 
         for x in xrange(beginrev, endrev, dist):
-            rl.revision(x)
+            # Old revisions don't support passing int.
+            n = rl.node(x)
+            rl.revision(n)
 
     timer, fm = gettimer(ui, opts)
     timer(d)