Fix browsing when invalid services present

Import patch from Arch to prevent service browsing from aborting in the middle if your network contains a device an invalid service name. See https://github.com/lathiat/avahi/issues/212 and https://bugs.archlinux.org/task/71781

I suffer from this problem! Either my oven or my washing machine stops CUPS from seeing my printer. I've confirmed this patch fixes it, and also restores avahi-browse functionality on the commandline.