FUEL ceph documentation need to be updated to add tmalloc fix steps

[Kostiantyn Danylov]

Need to add steps for tmalloc CPU consumption fix tot documentation.

On fast (SSD) disk ceph may start consuming a lot of CPU.
This can be tested with perf tools:

'perf top' should show a lot of tmalloc:: functions on top.
See https://mirantis.jira.com/projects/CEPH/issues/CEPH-180?filter=myopenissues for workaround description

[Fuel Devops McRobotson (fuel-devops-robot)]

Fix proposed to branch: master
Change author: Mariia Zlatkova <email address hidden>
Review: https://review.fuel-infra.org/28452

[Fuel Devops McRobotson (fuel-devops-robot)]

Reviewed: https://review.fuel-infra.org/28452
Submitter: Olga Gusarenko <email address hidden>
Branch: master

Commit: fd99503d3292bc2c5ac5951fc4f1f867a44c46eb
Author: Mariia Zlatkova <email address hidden>
Date: Wed Nov 16 15:29:42 2016

[Ceph Best Practices] Adds tmalloc fix steps

* Adds the "CPU and memory resources overconsumption" section
describing how to diagnose the issue. Also describes
the workaround.
* Adds minor editorial changes.

Change-Id: I100e8694729c46ca2bddf6fcbe243d6cc1cab0af
Closes-Bug: #1631913

[TatyanaGladysheva (tgladysheva)]

Verified on 9.2 snapshot #528.

New section "4.8 CPU and memory resources overconsumption" was added into Ceph Best Practices guide in https://infra-ci.fuel-infra.org/job/new.verify-mos-docs/145/MOS_documentation/ and in https://docs.mirantis.com/openstack/fuel/fuel-master/assets/CephBestPractices.pdf.