f_repobuild: Add remaining packages explicitly

f_repobuild: Add remaining packages explicitly

Packetary automatically solves for Fuel@OPNFV:
- base pkgs and their deps;
- bootstrap/target image additional pkgs;
- explicit reqs;

However, corner cases like "pcs", which is not in any of the
above categories - being installed via puppet only, need to be
added to the explicit list.

NOTE: This enables full offline deploys for simple scenarios
(i.e. without any plugins). Each plugin might need additional
packages, which will be handled in further patches.
See the bug report for more information.

JIRA: FUEL-250

Change-Id: Id1d31c98308cdee6cb935627984188561b560ff4
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>