Fix validator_test hang on Solaris, Plan 9

On these platforms, the `done <- true` statement in during TearDown() was
hanging, since the `watcher_unsupported.go` version was never draining the
channel. Also took the opportunity to update the WatchForUpdates() signature
to not return bool anymore.

validator.go

@@ -21,13 +21,10 @@ func NewUserMap(usersFile string, done <-chan bool, onUpdate func()) *UserMap {
 	atomic.StorePointer(&um.m, unsafe.Pointer(&m))
 	if usersFile != "" {
 		log.Printf("using authenticated emails file %s", usersFile)
-		started := WatchForUpdates(usersFile, done, func() {
+		WatchForUpdates(usersFile, done, func() {
 			um.LoadAuthenticatedEmailsFile()
 			onUpdate()
 		})
-		if started {
-			log.Printf("watching %s for updates", usersFile)
-		}
 		um.LoadAuthenticatedEmailsFile()
 	}
 	return um

watcher.go

@@ -30,7 +30,7 @@ func WaitForReplacement(filename string, op fsnotify.Op,
 	}
 }
 
-func WatchForUpdates(filename string, done <-chan bool, action func()) bool {
+func WatchForUpdates(filename string, done <-chan bool, action func()) {
 	filename = filepath.Clean(filename)
 	watcher, err := fsnotify.NewWatcher()
 	if err != nil {
@@ -65,5 +65,5 @@ func WatchForUpdates(filename string, done <-chan bool, action func()) bool {
 	if err = watcher.Add(filename); err != nil {
 		log.Fatal("failed to add ", filename, " to watcher: ", err)
 	}
-	return true
+	log.Printf("watching %s for updates", filename)
 }

watcher_unsupported.go

@@ -6,7 +6,7 @@ import (
 	"log"
 )
 
-func WatchForUpdates(filename string, done <-chan bool, action func()) bool {
+func WatchForUpdates(filename string, done <-chan bool, action func()) {
 	log.Printf("file watching not implemented on this platform")
-	return false
+	go func() { <-done }()
 }