Store only 4 ip addresses because 5 exceed the maximum length.
I've run into this now a couple of times and I'm concerned that others will too. It's unlikely to happen on our test phones, but on real ones it's quite easy to get 5 different ips (wifi at home, the office, partner, mcdonalds, public wifi, friends,...) and contact exchanges will indefinitely fail from that point.
fixes #885 (closed)
Signed-off-by: goapunk firstname.lastname@example.org