Removes 3PAR domain option from cinder config file

Removes 3PAR domain option from cinder config file

The HP 3PAR domain is no longer required to be specified in the
cinder configuration file. This patch automatically looks up the
domain using the Common Provisioning Group (CPG) specified.
hp3par_domain will remain in the config for now and will be
logged as deprecated. It will be removed in the I release.

DocImpact
Change-Id: I3ed01eed26209caa1904bec1f585059860294f38
Fixes: bug 1194599