terrform/openstack: Fix templating of ansible_ssh_common_args in...

terrform/openstack: Fix templating of ansible_ssh_common_args in no_floating.yml if used as TF module (#8646)

* terraform/openstack: Use path.module for ansible_bastion_template.txt

This extends on #7643 by not using path.root, but switching to path.module
to allow use of the terraform code as a module itself. This change then keeps
all calls to the template file stable even for that use-case.

* terraform/openstack: Make sed calls fail on errors

By using a single call with two replacements to use of sed will create proper exit codes
and allowing for errors to be recognized by terraform.