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/exec.go

@@ -26,7 +26,6 @@ import (
 	"os/exec"
 	"strings"
 
-	"github.com/purpleidea/mgmt/event"
 	"github.com/purpleidea/mgmt/util"
 
 	errwrap "github.com/pkg/errors"
@@ -98,7 +97,7 @@ func (obj *ExecRes) BufioChanScanner(scanner *bufio.Scanner) (chan string, chan
 }
 
 // Watch is the primary listener for this resource and it outputs events.
-func (obj *ExecRes) Watch(processChan chan *event.Event) error {
+func (obj *ExecRes) Watch() error {
 	var send = false // send event?
 	var exit *error
 	bufioch, errch := make(chan string), make(chan error)
@@ -141,7 +140,7 @@ func (obj *ExecRes) Watch(processChan chan *event.Event) error {
 	}
 
 	// 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...
 	}
 
@@ -174,7 +173,7 @@ func (obj *ExecRes) Watch(processChan chan *event.Event) error {
 			send = false
 			// it is okay to invalidate the clean state on poke too
 			obj.StateOK(false) // something made state dirty
-			obj.Event(processChan)
+			obj.Event()
 		}
 	}
 }