Stop sourcing devtest_undercloud.

Like devtest_seed, we need endpoint details and noproxy settings as
outputs from the undercloud script. By moving them into the structured
testenvironment file we can query them later without depending on an
ever moving set of environment variables. This will also support using
pre-running underclouds to run overcloud tests in CI (when we get to
that).

Change-Id: Ida6beac05c46ab5c7da8a77ae3a14fec5a39a825
When debugging setup-endpoints set -x as well.

This gives more insight into whatever goes wrong when debugging is
requested.

Change-Id: I9099e0ca404c7813e9761f37842fafc90230818a
Minor syntax cleanup in devtest.sh.

Prep work for re-integrating the docs.

Change-Id: Id99166d5641ed446af5d0b743fb54db170109a08