Ignore 'Printer-added' notifications for queues created by cups-browsed

Hi,

there are Ubuntu reports - 1869981 1878241 - about duplicate notifications for print queues, which are created by cups-browsed. The duplicate notifications appear when cups-browsed is restarted for a brief moment, e.g. logrotate, cupsd restart, and can be annoying for users.

Since it is not possible to recognize whether notifications for cups-browsed queues are valid or not, in my opinion the best course of action is to ignore them.

The patch is using 'cups-browsed' option, which is in every cups-browsed managed queue - gsd will not create a notification for a queue which has the option set to 'on'/'true'/'yes'. Since cups-browsed connects only to local cupsd when creating queues (so its queues are only on local cupsd), it makes sense to use CUPS_HTTP_DEFAULT in cupsGetNamedDest() call - it stands for localhost. Either way the new function - is_cupsbrowsed_dest() - is called in a condition where it is in AND relation with is_local_dest(), so even if a dest wouldn't be a local one, shortened evalution will not call the new function.

Please let me know whether I should change something.

If it is okay, would you mind adding the patch to the project?

I tested it manually (I'm not sure whether g-s-d has a test-suite for it) - I added a new printer via control-center, notification was shown with old and patched g-s-d, then started cups-browsed and old g-s-d showed a notification and the patched didn't.

Thank you in advance!

Zdenek