Kernel parameters -- how to set

New section in Operations Guide
This section includes info about using Cobbler web UI.

User Guide: new section for Settings/kernel parameter

Removed details from iommu section in Release Notes and replaced
it with an xref to the new section in Ops Guide

Change-Id: I0870c636f241ec83b1ce02873d20251281e29b35
Partial-Bug: 1324483
Partial-Bug: 1359494
Merge "Kernel parameters -- how to set"