plugin/forward: move Dial goroutine out (#1738)

Rework the TestProxyClose - close the proxy in the *same* goroutine
as where we started it. Close channels as long as we don't get dataraces
(this may need another fix).

Move the Dial goroutine out of the connManager - this simplifies things
*and* makes another goroutine go away and removes the need for connErr
channels - can now just be dns.Conn.

Also:

Revert "plugin/forward: gracefull stop (#1701)"
This reverts commit 135377bf77.

Revert "rework TestProxyClose (#1735)"
This reverts commit 9e8893a0b5.

plugin/forward/proxy.go

@@ -24,9 +24,6 @@ type Proxy struct {
 	fails uint32
 
 	avgRtt int64
-
-	state      uint32
-	inProgress int32
 }
 
 // NewProxy returns a new proxy.
@@ -85,26 +82,15 @@ func (p *Proxy) Down(maxfails uint32) bool {
 	return fails > maxfails
 }
 
-// close stops the health checking goroutine and connection manager.
+// close stops the health checking goroutine.
 func (p *Proxy) close() {
-	if atomic.CompareAndSwapUint32(&p.state, running, stopping) {
-		p.probe.Stop()
-	}
-	if atomic.LoadInt32(&p.inProgress) == 0 {
-		p.checkStopTransport()
-	}
+	p.probe.Stop()
+	p.transport.Stop()
 }
 
 // start starts the proxy's healthchecking.
 func (p *Proxy) start(duration time.Duration) { p.probe.Start(duration) }
 
-// checkStopTransport checks if stop was requested and stops connection manager
-func (p *Proxy) checkStopTransport() {
-	if atomic.CompareAndSwapUint32(&p.state, stopping, stopped) {
-		p.transport.Stop()
-	}
-}
-
 const (
 	dialTimeout = 4 * time.Second
 	timeout     = 2 * time.Second
@@ -112,9 +98,3 @@ const (
 	minTimeout  = 10 * time.Millisecond
 	hcDuration  = 500 * time.Millisecond
 )
-
-const (
-	running = iota
-	stopping
-	stopped
-)