Mark zgb as unimportant, as the builder is gone.
Mark zgb as unimportant, as the builder is gone.

BUG=chromium-os:25443
TEST=cbuildbot_config_unittest.py

Change-Id: I42bc10a953bcba3795d422e3ded374d9647f5420
Reviewed-on: https://gerrit.chromium.org/gerrit/14750
Reviewed-by: Chris Sosa <959d3d631fb6f17f1b07f751372041a1edb210d1@chromium.org>
Tested-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>

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