Fix cbuildbot_commands_unittest.py to work again.
Fix cbuildbot_commands_unittest.py to work again.

BUG=chromium-os:24498
TEST=Verify cbuildbot_commands_unittest passes again.

Change-Id: If2018b23f3d463af03914fb87477348da4c61072
Reviewed-on: https://gerrit.chromium.org/gerrit/13379
Commit-Ready: Ryan Cui <5ce1592d53754a87a44fc2eb7b63d5f77cf50fdb@chromium.org>
Reviewed-by: Ryan Cui <5ce1592d53754a87a44fc2eb7b63d5f77cf50fdb@chromium.org>
Tested-by: Ryan Cui <5ce1592d53754a87a44fc2eb7b63d5f77cf50fdb@chromium.org>

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