(com)mon: pick addresses based on whether we want public, cluster or both addresses

This patch set adds the following commits:

- Add mandatory mask to pick_addresses() on common/pick_address.h, and add 2 defines: one for a public address and other for cluster address;
- Use solely PUBLIC on ceph-mon
- Use PUBLIC|CLUSTER on ceph-osd, ceph-mds and ceph-syn (i.e., where pick_addresses() is used.