Create zuul.executor.hostname ansible variable

It will be helpful to know which executor ansible-playbook is run
from so pass this info into vars.yaml.

Additionally, update our test_v3 playbook test to also validate our
other executor ansible variables.

Change-Id: I22091c8e764ad519878e5d530e5bc72ffd2a4870
Signed-off-by: Paul Belanger <pabelanger@redhat.com>
6 files changed