Don't start the browser on restarts (fixes #636)

cmd/syncthing/monitor.go

@@ -86,7 +86,7 @@ func monitorMain() {
 			cmd.Process.Kill()
 			<-exit
 			return
-		case <-exit:
+		case err = <-exit:
 			if err == nil {
 				// Successfull exit indicates an intentional shutdown
 				return
@@ -95,6 +95,10 @@ func monitorMain() {
 
 		l.Infoln("Syncthing exited:", err)
 		time.Sleep(1 * time.Second)
+
+		// Let the next child process know that this is not the first time
+		// it's starting up.
+		os.Setenv("STRESTART", "yes")
 	}
 }