xci: Change cinder backend and move nfs to compute00

xci: Change cinder backend and move nfs to compute00

This change
- switches cinder backend from lvm to nfs as examplified in [1].
- moves nfs shares from compute01 to compute00 in order to merge
configure-targethosts.yml playbook in upcoming change.
- updates openstack_user_config.yml to reflect the switch to nfs
and move of nfs server to compute00.
- removes exports file due to switching to lineinfile module.

[1] https://docs.openstack.org/project-deploy-guide/openstack-ansible/draft/app-config-prod.html

Change-Id: I0715c98a89ab124256e3857c1047e374f261e39b
Signed-off-by: Fatih Degirmenci <fatih.degirmenci@ericsson.com>