fix bug to get service plan in lifecycle test

Change-Id: Iad4ed8f36db9e656824445faf8c28230a8556e9f
Reviewed-on: http://reviews.cloudfoundry.org/13636
Tested-by: CI Master <cf-ci@rbcon.com>
Reviewed-by: Frank Lu <flu@vmware.com>
Reviewed-by: Nicholas Kushmerick <nicholask@vmware.com>