[openstack] Fix Test

There seems to be a difference in results coming from these two:

export FOG_MOCK=true && bundle exec shindont +openstack
FOG_MOCK=true shindo tests/openstack/requests/compute/security_group_tests.rb

Signed-off-by: Nelvin Driz <nelvindriz@live.com>

lib/fog/openstack/requests/compute/create_security_group.rb

@@ -23,6 +23,7 @@ module Fog
 
       class Mock
         def create_security_group(name, description)
+          Fog::Identity.new(:provider => 'OpenStack')
           tenant_id = Fog::Identity::OpenStack::Mock.data[current_tenant][:tenants].keys.first
           security_group_id = Fog::Mock.random_numbers(2).to_i
           self.data[:security_groups][security_group_id] = {

lib/tasks/test_task.rb

@@ -8,7 +8,7 @@ module Fog
       def initialize
         desc "Run the mocked tests"
         task :test do
-          Rake::Task[:mock_tests].invoke
+          ::Rake::Task[:mock_tests].invoke
         end
 
         task :mock_tests do