disco: Add Name method to Service object (#233)

This will help with logging in apps that use this module.

disco/disco.go

@@ -482,6 +482,11 @@ func (s *Service) ServiceInstances() (ret []ServiceInstance) {
 	return ret
 }
 
+// Name of the service
+func (s *Service) Name() string {
+	return s.name
+}
+
 // ForceInstances overrides a disco service to have exactly the passed instances forever.  Useful
 // for debugging.
 func (s *Service) ForceInstances(instances []ServiceInstance) {

disco/disco_test.go

@@ -348,6 +348,7 @@ func testServices(t *testing.T, z1 zktest.ZkConnSupported, ch <-chan zk.Event, z
 	require.NoError(t, err)
 	require.Equal(t, 0, len(s.ServiceInstances()))
 	require.NotNil(t, s.StateLog())
+	require.Equal(t, "not_here", s.Name())
 
 	onWatchChan := make(chan struct{})
 	s.Watch(func() {