Assert there are no policies

The policies are optimized dow in the C code, they get instanciated only
upon request. We need to get something like
xccdf_policy_model_get_all_policies. To iterate through all meaningful
policies within benchmark+tailoring.

Author: isimluk

test/xccdf/policy_test.rb

@@ -21,6 +21,8 @@ def test_new_policy_model
     @s = OpenSCAP::Source.new '../data/xccdf.xml'
     b = OpenSCAP::Xccdf::Benchmark.new @s
     pm = OpenSCAP::Xccdf::PolicyModel.new b
+    assert !b.nil?
+    assert pm.policies.size == 0, pm.policies.to_s
     pm.destroy
   end
 end