Add central agent HA and workload partitioning

Currentrly ceilometer central agent is the only one ceilometer component that didn't support HA and workload partitioning. During Juno release cycle this feature was intorduces to the ceilometer in the upstream code using tooz coordination openstack library. This library supports several backends (zookeeper, redis, memcached among them). It was decided to introduce this built-in ceilometer feature to MOS as well. Redis was chosen as the coordination backend.
We've decided to implements this feature as experimental, so it'll be fuel-plugin.

This feature implementation requires following things to be done:
1. Implement redis installation
2. Redis packages
3. Configure ceilometer central agents to work with redis

Upstream specs for this change: https://github.com/openstack/ceilometer-specs/blob/master/specs/juno/central-agent-partitioning.rst
Upstream redis puppets to be used as basis: https://github.com/fsalum/puppet-redis

Feature lead: Dina Belova
Mandatory Design Reviewers: Vladimir Kuklin, Sergii Golovatiuk
Developers: Ivan Berezovskiy, Dina Belova
QA: Vadim Rovachev