[mos-xenial] Fuel-agent: changes for implement Ubuntu Xenial Xerus support

[Ivan Suzdal]

According to https://blueprints.launchpad.net/fuel/+spec/support-ubuntu-xenial-xerus we need to make a small changes in fuel-agent project.

In my opinion:
1) package naming (e.g.: linux-{headers,image}-generic-lts-CODENAME in DEFAULT_TRUSTY_PACKAGES)
2) _probably_, DEFAULT_TRUSTY_PACKAGES should be renamed to DEFAULT_UBUNTU_PACKAGES
3) also, codename/suite in tests
4) fuel_bootstrap/files/xenial can be copied from uel_bootstrap/files/trusty (don't forget about mcollective daemonize)

During investigation I've been found that mcollective shall be deamonized (or service type, in systemd notation, shall be simple instead of forking). Also, cloud-init-templates require some changes related to rc.local (missing shebang will cause 'unknown exec format' systemd error), and mcollective settings (daemonize parameter).

UPD: The following CRs found to be useful to build custom ISO based on 16.04:
* https://review.openstack.org/#/c/332126/
* https://review.openstack.org/#/c/332203/

They should be re-implemented if needed to match component development plan.

[Dmitry Teselkin (teselkin-d)]

This becomes a blocker for migration to Ubuntu Xenial - we have to patch env in place and it doesn't look like someone is working on a fix.

[Dmitry Pyzhov (dpyzhov)]

This is a part of the blueprint. Why should it be tracked as a separate bug?