common/ipaddr: Allow binding on lo

common/ipaddr: Allow binding on lo

Commmit 5cf0fa872231f4eaf8ce6565a04ed675ba5b689b, solves the issue that
the osd can't restart after seting a virtual local loopback IP. However,
this commit also prevents a bgp-to-the-host over unumbered Ipv6
local-link is setup, where OSD typically are bound to the lo interface.

To solve this, this single char patch simply checks against "lo:" to
match only virtual interfaces instead of anything that starts with "lo".

Fixes: https://tracker.ceph.com/issues/48893
Signed-off-by: Thomas Goirand <zigo@debian.org>