fix halt when player is removed

rewritten without goroutines or checking if processes exist and it seems
to work much better now.

go.mod

@@ -2,6 +2,4 @@ module github.com/hrfee/waybar-mpris
 
 go 1.15
 
-require (
-	github.com/godbus/dbus/v5 v5.0.3
-)
+require github.com/godbus/dbus/v5 v5.0.3