Remove src/libs/zeroconf

The code has been unused for a while and shows up in the static
analyzer.

Change-Id: I7b59be985d7e6e140eaee217978660b767e7b11c
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>