accountmodel: fix Ring contacts not showing up

This fixes the contacts with RingIDs being hidden in the
CategorizedContactModel when setUnreachableHidden is true. This was
due to a regression introduced in an earlier patch which made it
that only the SIP protocol was marked as enabled and only if there
was an IP2IP account.

Change-Id: Ia59c5c6826fdc8cf2513807685204b2b38072ba9
Tuleap: #720