Revert "Install RabbitMQ 3.5.4 on Ubuntu systems"

This reverts commit 9da87065f5.
Packaging [1] is fixed now.

[1] http://www.rabbitmq.com/releases/rabbitmq-server/v3.5.5/

Change-Id: Ibb3b108432b8bcf76a54bf8dd6f7f61616d8ced1

install_modules.sh

@@ -57,11 +57,6 @@ if type "apt-get" 2>/dev/null; then
     # apt-get update needs to be run to be able (later) to install
     # ubuntu-cloud-keyring package with puppet
     /usr/bin/apt-get update
-
-    # install rabbitmq-server from ubuntu repository until
-    # rabbitmq repository contains the fix mentionned in:
-    # https://github.com/rabbitmq/rabbitmq-server/issues/321
-    /usr/bin/apt-get install -y rabbitmq-server
 else
     # disable SElinux
     # something is python-cffi is preventing Nova & Keystone to