InputScenarioUtils load images if glance available

The scenario_images utility of InputScenarioUtils shall
load the image list from glance only if glance is available.
Otherwise the test discovery process will fail if glance
is not available.

Closes bug 1277669

Change-Id: I4be7b9b88d9f8ff42059ece84a3c58df4fb90f1e
Network API: default to ipv4, add ipv6 tests

Change-Id: I34da0ede4d7b92b2e752c2da82172c495e1946b1
Add extra list servers by host test

Add list servers by existent host

Change-Id: I287ac53709beb8274f9abf6a5b2ad51503a7f49d
Merge "InputScenarioUtils load images if glance available"
Merge "Network API: default to ipv4, add ipv6 tests"
Merge "Add extra list servers by host test"
Merge branch 'master' of https://github.com/openstack/tempest