The Monasca Agent collects metrics and in this change is deployed
across the control plane. These metrics are collected into an OpenStack
project. It supports configuring a small number of plugins, which can
be extended in later commits. It also makes the Monasca Agent credentials
available to other roles, such as the common role to allow forwarding
logs to Monasca.

Partially-Implements: blueprint monasca-roles
Change-Id: I76b34fc5e1c76407a45fcf272268d5798b473ca2