Add oldrev/newrev column to the buildset reporter table

This change adds oldrev/newrev column to the zuul_buildset sql table to
be able to query post job for a specific commit.

Change-Id: Ic9c0b260560123d080fa47c47a76fcfa31eb3607
diff --git a/tests/unit/test_connection.py b/tests/unit/test_connection.py
index de3b7cf..6815f83 100644
--- a/tests/unit/test_connection.py
+++ b/tests/unit/test_connection.py
@@ -69,7 +69,7 @@
         insp = sa.engine.reflection.Inspector(
             self.connections.connections['resultsdb'].engine)
 
-        self.assertEqual(11, len(insp.get_columns(buildset_table)))
+        self.assertEqual(13, len(insp.get_columns(buildset_table)))
         self.assertEqual(10, len(insp.get_columns(build_table)))
 
     def test_sql_results(self):