When executing the check for the appropriate files on
the repo host and then overriding the group_vars to
cater for when the repo is not present, we need to make
sure that we're doing the checks against the right URL.
In this patch we backup the default URL so that it can
be used when re-executing the check later in the same
playbook.
Also, given that the set-pip-upstream-url.yml and
set-upper-constraints.yml task sets are always used
together, we combine them into one task set.
Depends-On: https://review.openstack.org/563578
Change-Id: I040c4f5b6e96c85c68beb975f7b80d1edf42276d
792c753354