Use nova_metadata related hiera and make cell aware
Use nova_metadata related hiera and make cell aware

Since nova metadata runs via wsgi and can be run on its own
use nova_metadata_ related hiera keys to configure the
proxy in haproxy.
It is now also possible to configure nova_metadata local
to a nova cellv2.

Change-Id: I364436ed6ca451dfaa079dc891c2cb6516eb3907
Related-Bug: #1823760

openstack/puppet-tripleo,openstack/puppet-tripleo,openstack/puppet-tripleo