Now that the underlying images are correctly being built for arm,
we see that several dependencies are missing wheels, and compiling
them under emulation takes a very long time. Until we resolve that,
only build container images for amd64.
When devstack is enabled with TLS support
(If607caf301211181b4f37a2c7012f875de3d285c) the cloud config has a
reference to the CA in /opt/stack/data; thus we need to map it into
the builder/launcher container. We missed this with testing in
Iacc71e9e744249c7ce585ab7131cc9e905d600ff because the image build
failed and thus the container-based job didn't run.
Change-Id: Ica9aecd457f8b6abcfd3cdbdb425d411f98ffeff
c31dc75912