Fix rspec 3.x syntax

- Convert 'should' keyword to 'is_expected.to',
- The old ':should' syntax in rspec 3.x is deprecated in favor of ':expect'
  syntax,
- Expectations on attribute of subject with 'its'.

Change-Id: I99d7819595a51c16b0b82122d75c0a6ebfad7907
Signed-off-by: Gael Chamoulaud <gchamoul@redhat.com>

spec/acceptance/designate_config_spec.rb

@@ -43,11 +43,14 @@ describe 'basic designate_config resource' do
     end
 
     describe file('/etc/designate/designate.conf') do
-      it { should exist }
-      it { should contain('thisshouldexist=foo') }
-      it { should contain('thisshouldexist2=<SERVICE DEFAULT>') }
+      it { is_expected.to exist }
+      it { is_expected.to contain('thisshouldexist=foo') }
+      it { is_expected.to contain('thisshouldexist2=<SERVICE DEFAULT>') }
 
-      its(:content) { should_not match /thisshouldnotexist/ }
+      describe '#content' do
+        subject { super().content }
+        it { is_expected.to_not match /thisshouldnotexist/ }
+      end
     end