Add more roles to designate formulas

Provide roles:
pool_manager
worker
agent

The idea was proposed by Aleš Komárek:
https://gerrit.mcp.mirantis.net/6723

Make adjustments to designate.conf.Debian to be able
to take into account pool_manager changes in
reclass model.

Provide default roles description in pillars for tests.

Change-Id: I214d8db39365648b5ef9348b52edd839327ca197
Related-PROD: https://mirantis.jira.com/browse/PROD-14396
10 files changed