resources, pgraph: Refactor Worker and simplify API

I'm still working on reducing the size of the monster patches that I
land, but I'm exercising the priviledge as the initial author. In any
case, this refactors worker into two, and cleans up the passing around
of the processChan. This puts common code into Init and Close.

resources/nspawn.go

@@ -23,7 +23,6 @@ import (
 	"fmt"
 	"log"
 
-	"github.com/purpleidea/mgmt/event"
 	"github.com/purpleidea/mgmt/util"
 
 	systemdUtil "github.com/coreos/go-systemd/util"
@@ -98,7 +97,7 @@ func (obj *NspawnRes) Init() error {
 }
 
 // Watch for state changes and sends a message to the bus if there is a change
-func (obj *NspawnRes) Watch(processChan chan *event.Event) error {
+func (obj *NspawnRes) Watch() error {
 	// this resource depends on systemd ensure that it's running
 	if !systemdUtil.IsRunningSystemd() {
 		return fmt.Errorf("Systemd is not running.")
@@ -122,7 +121,7 @@ func (obj *NspawnRes) Watch(processChan chan *event.Event) error {
 	bus.Signal(buschan)
 
 	// notify engine that we're running
-	if err := obj.Running(processChan); err != nil {
+	if err := obj.Running(); err != nil {
 		return err // bubble up a NACK...
 	}
 
@@ -155,7 +154,7 @@ func (obj *NspawnRes) Watch(processChan chan *event.Event) error {
 		// do all our event sending all together to avoid duplicate msgs
 		if send {
 			send = false
-			obj.Event(processChan)
+			obj.Event()
 		}
 	}
 }