Adds a description of provider network vs tenant networks

In this commit we have include a paragraph to describe the
differences between provider vs tenant networks.
The description of all provider network types is already covered
in this cloud admin guide

Closes Bug: 1087586

Change-Id: I18b1c53ffaff8e878da9fb1f9e14c8f6c5da2491
Merge "Adds a description of provider network vs tenant networks"