Report graphics port after resolving (#1622)

Allow libvirt to start the domain before reading back the XML to
retrieve the port assigned automatically for subsequent graphics access
when autoport is enabled.

Fixes: #992

spec/unit/action/start_domain_spec.rb

@@ -34,6 +34,7 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
 
       allow(logger).to receive(:debug)
       allow(logger).to receive(:info)
+      allow(ui).to receive(:info)
 
       allow(libvirt_domain).to receive(:xml_desc).and_return(domain_xml)
 
@@ -162,6 +163,28 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
       end
     end
 
+    context 'graphics' do
+      context 'autoport not disabled' do
+        let(:test_file) { 'existing.xml' }
+        let(:launched_domain_xml) {
+          new_xml = domain_xml.dup
+          new_xml.gsub!(/graphics type='vnc' port='-1'/m, "graphics type='vnc' port='5900'")
+          new_xml
+        }
+
+        it 'should retrieve the port from XML' do
+          expect(ui).to_not receive(:warn)
+          expect(connection).to_not receive(:define_domain)
+          expect(libvirt_domain).to receive(:xml_desc).and_return(domain_xml, launched_domain_xml)
+          expect(libvirt_domain).to receive(:autostart=)
+          expect(domain).to receive(:start)
+          expect(ui).to receive(:info).with(' -- Graphics Port:     5900')
+
+          expect(subject.call(env)).to be_nil
+        end
+      end
+    end
+
     context 'nvram' do
       context 'when being added to existing' do
         let(:vagrantfile_providerconfig) do