[doc] Update troubleshooting section of ops guide for the HA AMQP cluster

[Bogdan Dobrelya]

Provide exact commands for an admin to run to diagnose (and/or) exact messages to look for in the logs:
1. Check if there is a problem in Corosync/Pacemaker layer
2. Check if there is a problem in the RabbitMQ layer
3. Check if there is a problem in the Oslo.messaging layer
4. Check if there are problems with any of the components (Nova, Neutron etc)

Then steps to remediate:
A. How to recover from #1 above
B. How to recover from #2 above
C. How to recover from #3 above
D. How to recover from #4 above

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/184014

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/184014
Committed: https://git.openstack.org/cgit/stackforge/fuel-docs/commit/?id=476483fdae835495dbe1bb4f525ca624915069b0
Submitter: Jenkins
Branch: master

commit 476483fdae835495dbe1bb4f525ca624915069b0
Author: Bogdan Dobrelya <email address hidden>
Date: Mon May 18 12:53:18 2015 +0200

    Describe basic checks and recovery steps for AMQP issues.

    This brings new section into the ops guide, which describes
    how to check and recover AMQP issues in Mirantis OpenStack environments
    deployed by Fuel.

    Closes-bug: #1456082

    Change-Id: I73e6d4fce336911406272f8c537f7003fdb1b5bb
    Signed-off-by: Bogdan Dobrelya <email address hidden>