Fix returncode check in cbuildbot to actually check the return code.
Fix returncode check in cbuildbot to actually check the return code.

BUG=chromium-os:18891
TEST=Ran it, checked exit code of caller

Change-Id: Ic9e46a7bfe494a96ad232b97ac4b9afd9200dac1
Reviewed-on: https://gerrit.chromium.org/gerrit/11672
Reviewed-by: Chris Sosa <959d3d631fb6f17f1b07f751372041a1edb210d1@chromium.org>
Tested-by: Chris Sosa <959d3d631fb6f17f1b07f751372041a1edb210d1@chromium.org>
Reviewed-by: Don Garrett <546ec366615570e68497e3c5df9092106a9808f4@chromium.org>

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