Fix refresh-packages builder after recent refactoring.
Fix refresh-packages builder after recent refactoring.

The recent refactoring at https://gerrit.chromium.org/gerrit/#change,11193
broke the refresh-packages builder by making it follow the same
flow as the SDK builder.  This should fix it.

BUG=None
TEST=Will be tested as soon as this goes live.  No hurry.
In the meantime I'll run refresh_packages manually.

Change-Id: I7264780e8061b560858689c0fa52f489f59855ec
Reviewed-on: https://gerrit.chromium.org/gerrit/11490
Tested-by: Matt Tennant <46e612415b446ccde19638e4035892001c237942@chromium.org>
Reviewed-by: Chris Sosa <959d3d631fb6f17f1b07f751372041a1edb210d1@chromium.org>
Commit-Ready: Matt Tennant <46e612415b446ccde19638e4035892001c237942@chromium.org>

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