Add cleaned up Gerrit props to properties.test_api.tryserver.

recipe_modules/properties/example.expected/buildbot_tryserver_gerrit_override_both.json

 [
   {
     "cmd": [
       "echo",
       "None",
       "'thing'"
     ],
     "name": "echo"
   },
   {
     "cmd": [
       "echo",
       "('blamelist', ['cool_dev1337@chromium.org', 'hax@chromium.org'])",
       "('buildbotURL', 'http://c.org/p/cr/')",
       "('buildername', 'TestBuilder')",
       "('buildnumber', 571)",
       "('foo.bar-bam', 'thing')",
       "('mastername', 'chromium.testing.master')",
+      "('patch_branch', 'master')",
+      "('patch_gerrit_url', 'https://gerrit.my.host')",
+      "('patch_issue', 4455)",
+      "('patch_project', 'custom')",
+      "('patch_ref', 'refs/changes/89/456789/12')",
+      "('patch_repository_url', 'https://git.my.host/custom')",
+      "('patch_set', 12)",
+      "('patch_storage', 'gerrit')",
       "('recipe', 'properties:example')",
       "('slavename', 'TestSlavename')",
       "('test_prop', None)",
       "('workdir', '/path/to/workdir/TestSlavename')"
     ],
     "name": "echo all"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]