Add cluster support for rabbitmq element

Nodes can be joined into rabbitmq cluster now. This
patch sets up firewall, makes sure that hostname translation works
for rabbitmq nodes and automates adding nodes into cluster. See
rabbitmq-server/README for more details.

Change-Id: Idfb0a168fd2fd19b8fca4fa410c79091b636d79b
Fix rabbitmq env file name and log path

Proper filename for setting env vars is rabbitmq-env.conf, otherwise
rabbitmqctl is not able to connect to the server on newly deployed
undercloud or overcloud.

Change-Id: I53b3df2fbe0f3da976b32dbeed9a6277fd1c38bc
Update openstack config files to support rabbitmq cluster

Change-Id: I178b861a22813154df584502eee145b6474d4573
Enable iscsid on openSUSE

Services are not automatically enabled after installation on openSUSE. iscsid
is required to run for nova-baremetal.

Change-Id: I1d5431ad1ac89ead5c6a1b609a79d1491c97cf27
Fix compatibility link creation for mysql.sock on openSUSE

Create the /var/run/mysql/mysql.sock compatibility link already during the
pre-configure run. Otherwise e.g. the "reset-db" script called during the
"boot-stack" element's configure run will fail to find the mysql socket.

Change-Id: I8046f8d056e7d28e046ccfdfd22f6b73338352b6
Merge "Enable iscsid on openSUSE"
Merge "Fix compatibility link creation for mysql.sock on openSUSE"
Merge "Add cluster support for rabbitmq element"
Merge "Fix rabbitmq env file name and log path"
Merge "Update openstack config files to support rabbitmq cluster"