Use all roles to build out host groups

Prevously it was using node.run_list.roles when doing the intersection.
This was resulting in nodes not being listed across all host groups,
which then becomes a bit tricky when setting up monitoring via hostgroup.

For instance we want to monitor 'openstack-volume-api', but c1r1 was
not listed in that hostgroup.

Will work on getting this upstreamed.  Hell, if they build out hostgroups
for every role, why not add each node to it :/...
Merge pull request #6 from retr0h/working

Use all roles to build out host groups