group_vars: Refactor provisioner/bifrost

This change refactors bifrost provisioner playbooks and
roles to use group_vars instead of using vars from
engine/engine/var directory.

As bifrost/provision.sh is run on localhost initially,
it uses the newly created inventory file, localhost.ini,
to enable the use of group_vars. In the last command of
bifrost/provision.sh, bifrost_inventory.py is copied to
engine/engine/inventory to access to group_vars so the
the new full inventory file, inventory.ini, to use during
stack installation can be generated.

See the first change in series for the reasoning of
switching to group_vars which has additional information
as well.

Change-Id: I0cc76c2d2e1fb3b192e395c64f5df476b68a9200
diff --git a/playbooks/roles/install-configure-bifrost/tasks/main.yml b/playbooks/roles/install-configure-bifrost/tasks/main.yml
index 1befc88..8379e6b 100644
--- a/playbooks/roles/install-configure-bifrost/tasks/main.yml
+++ b/playbooks/roles/install-configure-bifrost/tasks/main.yml
@@ -16,6 +16,7 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 # ============LICENSE_END=========================================================
+
 - include_tasks: cleanup-bifrost.yml
 
 - name: Clone bifrost repository and checkout '{{ bifrost_version }}'