This patches adds changes to the Nova REST API to allow
users to create a server with a description, rebuild
a server with a description, update the description,
and get the description in the server details.
Note: Future commits will be done to support the server
description in python-novaclient and openstack-client.
APIImpact
Implements blueprint: user-settable-server-description
Change-Id: I74b1a340c5ab98fdea2186e87dd13f42ce7c7661