Introduces a keepalived manager for HA

This patch introduces a keepalived manager
which will be used for the blueprint
blueprint l3-high-availability.

The manager can create a keepalived.conf compliant configuration,
start, stop and restart the service, as well as create keepalived
notification scripts.

Implements: blueprint l3-high-availability
Change-Id: I1ba9f332778f27de950d9e97d4fb4a337f6f26da
Co-Authored-By: Assaf Muller <amuller@redhat.com>
Merge "Introduces a keepalived manager for HA"