skip collecting built artifacts in packaging test job
skip collecting built artifacts in packaging test job

We don't need to collect and sign the artifacts in the job that tests
building python packages.

Change-Id: I8b0db281b759fea668fd47c170c999d0b566e92f
Signed-off-by: Doug Hellmann <0798ebecfb7bc4dfb9d0445c2fa030eb64e1fa1c@doughellmann.com>

openstack-infra/project-config,openstack-infra/project-config