Revert GS storage for private bots.
Revert GS storage for private bots.

Private bots don't have access to default gs.

BUG=None
TEST=unittests

Change-Id: I1b132cf6a6115506e47e1ae36aa90a1f4691d055
Reviewed-on: http://gerrit.chromium.org/gerrit/7763
Reviewed-by: Scott Zawalski <d0bc454f32175e2361d26fbdb5930ff6be11acc5@chromium.org>
Tested-by: Peter Mayo <3d31fdaf44dc55bb1b4f50b19df9bc879177d37a@chromium.org>

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