Add custom filters for checking services

These filters can be used to capture a lot of the logic that we
currently have in 'when' statements, about which services are enabled
for a particular host.

In order to use these filters, it is necessary to install the
kolla_ansible python module, and not just the dependencies listed in
requirements.txt. The CI test and quickstart install from source
documentation has been updated accordingly.

Ansible is not currently in OpenStack global requirements, so for unit
tests we avoid a direct dependency on Ansible and provide fakes where
necessary.

Change-Id: Ib91cac3c28e2b5a834c9746b1d2236a309529556