Add reference to LP bug in configuration doc readme
Add reference to LP bug in configuration doc readme

Reference umbrella LP bug in readme for easier tracking of work
if someone wants to start working on dynamically generated
configuration docs.

Change-Id: Ic22b8acd9b3f9aaea61836b52df39ab10e040fba

mahak/cinder,openstack/cinder,mahak/cinder,openstack/cinder