make iso caching for comps.xml, ostf src zips

Download comps.xml into a different directory than repodata so that
createrepo doesn't delete it after it's done.

Use separate target for each OSTF source zip so that it's only
re-downloaded from Github when commit SHA changes, and not
unconditionally downloaded for every build.
Refactore create environment in HA deployment modes
Update assert result of run of OSTF in test cases
Add dummy test_ha_vlan_fence with 4 controllers

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>
Merge branch 'poc_fence'