resources: Simplify resource Converger and Startup code

This takes the Converged initialization and Startup patterns that are
common in all resources, and bakes it into the core engine. This way
resource writing is much more concise and there is less boilerplate!

resources/nspawn.go

@@ -22,7 +22,6 @@ import (
 	"errors"
 	"fmt"
 	"log"
-	"time"
 
 	"github.com/purpleidea/mgmt/event"
 	"github.com/purpleidea/mgmt/util"
@@ -101,17 +100,7 @@ func (obj *NspawnRes) Watch(processChan chan event.Event) error {
 	}
 	obj.SetWatching(true)
 	defer obj.SetWatching(false)
-	cuid := obj.converger.Register()
-	defer cuid.Unregister()
-
-	var startup bool
-	Startup := func(block bool) <-chan time.Time {
-		if block {
-			return nil // blocks forever
-		}
-		// 1/2 the resolution of converged timeout
-		return time.After(time.Duration(500) * time.Millisecond)
-	}
+	cuid := obj.Converger() // get the converger uid used to report status
 
 	// this resource depends on systemd ensure that it's running
 	if !systemdUtil.IsRunningSystemd() {
@@ -135,6 +124,11 @@ func (obj *NspawnRes) Watch(processChan chan event.Event) error {
 	buschan := make(chan *dbus.Signal, 10)
 	bus.Signal(buschan)
 
+	// notify engine that we're running
+	if err := obj.Running(processChan); err != nil {
+		return err // bubble up a NACK...
+	}
+
 	var send = false
 	var exit = false
 
@@ -165,16 +159,10 @@ func (obj *NspawnRes) Watch(processChan chan event.Event) error {
 		case <-cuid.ConvergedTimer():
 			cuid.SetConverged(true) // converged!
 			continue
-
-		case <-Startup(startup):
-			cuid.SetConverged(false)
-			send = true
-			obj.StateOK(false) // dirty
 		}
 
 		// do all our event sending all together to avoid duplicate msgs
 		if send {
-			startup = true // startup finished
 			send = false
 			if exit, err := obj.DoSend(processChan, ""); exit || err != nil {
 				return err // we exit or bubble up a NACK...