Ensures we can use FQDN in ceph.yml playbook

[cjeanner]

Until now, there was an inconsistency between the 06-deploy-edpm.yml and
06-deploy-architecture.yml playbooks when it comes to ceph
configuration:
in the first one, ceph.yml play was instructed to use FQDN (via
ansible_fqdn fact), while the latter was using shortnames (via
ansible_hostname).

This leads to issues whenever we want to set FQDN on the various nodes
and in the inventory, since some stages of the ceph configuration is
checking for name consistency.

As a pull request owner and reviewers, I checked that:

• Appropriate testing is done and actually running

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[fultonj]

This might be sufficient. cephadm's hostname handling is complex. Let's make sure delta and delta-ipv6 can pass with this before merging.

[cjeanner]

Seems we can remove all of those *_spec_fqdn and leverage inventory_hostname and its variations (item in loop).

This is implemented in #2164 . Closing this one.