Remove downloading undercloud.qcow2

Remove downloading undercloud.qcow2

OOO team is removing the undercloud disk image as it is no longer needed
for containerized undercloud deployments. Instead, we can just use the
overcloud image as the undercloud image.

Additionally, OOO team has recommended we use current-tripleo instead of
current-tripleo-rdo. current-tripleo-rdo was previously thought to be
more stable with more promotion checks, but now it seems that it is
older and current-tripleo now has the same stability/checks.

This patch also bumps the undercloud RAM from 8GB to 10GB. With the new
containerized undercloud there is more RAM consumption during
deployment.

Change-Id: I9e6bb2260dbe9f8796ee54d20527c0aad96476ec
Signed-off-by: Tim Rozet <trozet@redhat.com>