Add missing bit to the user prefetch removal.

Those are improvement based on last comment in the "Remove user/role
prefetch to support multi-domain.".  Namely:

  1. remove useless comments;
  2. improve the spec to reflect the actual error;

Change-Id: I1f622a14b41876be4b0b6d15cf78e28d76b6360e

lib/puppet/provider/keystone.rb

@@ -103,17 +103,6 @@ class Puppet::Provider::Keystone < Puppet::Provider::Openstack
     resource_to_name(*name_to_resource(name), false)
   end
 
-#  def self.roles_assignement_for_userid(user_id)
-#    unless @role_assignement_table
-#      @role_assignement_table = request('role assignment', 'list')
-#    end
-#    roles_id = []
-#    @role_assignement_table.each do |row|
-#      roles_id << row[:role] if row[:user] == user_id
-#    end
-#    roles_id
-#  end
-
   def self.user_id_from_name_and_domain_name(name, domain_name)
     @users_name ||= {}
     id_str = "#{name}_#{domain_name}"

spec/unit/provider/keystone_user/openstack_spec.rb

@@ -79,7 +79,9 @@ username="user1"
           described_class.expects(:openstack)
             .with('user', 'show', '--format', 'shell',
                   ['user1', '--domain', 'domain1_id'])
-            .returns('')
+            .twice
+            .raises(Puppet::ExecutionFailure,
+                    "No user with a name or ID of 'user1' exists.")
           expect(provider.exists?).to be_falsey
         end
       end