Fix cbuildbot_stages_unittest to pass again.
Fix cbuildbot_stages_unittest to pass again.

Followup to I7ab2128edf3b3ba3d4623c68186b2c35d05b7748.

BUG=chromium-os:32377
TEST=Verify cbuildbot_stages_unittest.py passes again.

Change-Id: I83d76b4d8d9271a5c726593a7cad4fc93dc23696
Reviewed-on: https://gerrit.chromium.org/gerrit/29885
Reviewed-by: Ryan Cui <5ce1592d53754a87a44fc2eb7b63d5f77cf50fdb@chromium.org>
Commit-Ready: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Tested-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>

coreos/chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,coreos/chromite,bpsinc-native/src_third_party_chromite,zhang0137/chromite,zhang0137/chromite,bpsinc-native/src_third_party_chromite,coreos/chromite,chadversary/chromiumos.chromite,zhang0137/chromite