Optimize: Replace 'fields.Enum' with 'object'
Optimize: Replace 'fields.Enum' with 'object'

We don't use any advanced features of 'versionobjects.fields.Enum'
in message fields. We can directly use 'object' there.

Change-Id: I3e2a7f52c8348ff6b1fb82d849a26c650236e78c

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