[DOC BLD FIX] Correct dosctring errors in disco driver
[DOC BLD FIX] Correct dosctring errors in disco driver

The docstring for version history at the top of the disco
driver wasn't properly formatted.  I put it in a text
code block to make it look better and to remove the
Spinx build WARNING.

Change-Id: Iebdc92fe155d634f61d29d099b3a216f9e173f0f

Datera/cinder,phenoxim/cinder,eharney/cinder,openstack/cinder,j-griffith/cinder,openstack/cinder,phenoxim/cinder,mahak/cinder,Datera/cinder,j-griffith/cinder,eharney/cinder,mahak/cinder