Revert "Use FQDN for rabbitmq's nodename env variable"
Revert "Use FQDN for rabbitmq's nodename env variable"

This seems to have broken the updates job, causing it to fail
with following error:

Can't set long node name!\nPlease check your configuration\n

Related-Bug: 1646873

This reverts commit 3e9fcfd09320ace07bc1bd4cb57feb98cd057332.

Change-Id: I72ba891cd9cd8c4f1bc204144f46aaabbdfd3647

dprince/tripleo-heat-templates,dprince/tripleo-heat-templates,openstack/tripleo-heat-templates,openstack/tripleo-heat-templates