Fixes personality support in Rackspace ASG resource

The Rackspace ASG API expects server personality to be defined
as an Array of dicts. It was being passed as a flat dict which
caused all creations of ASG resources to fail if a personality
was defined.

Change-Id: Idf0c1e8898a613f9b979312e080200dcc28cc7e9
Closes-Bug: #1322675