Object server wont start if the ring contains hostnames and servers_per_port is enabled

[david courtois]

setting hostnames instead of IP in the ring isn't an issue, but when enabling servers_per_port the object server silently loops reading the ring and doesn't bind to any interface.
to reproduce on SAIO :
set "export SERVERS_PER_PORT=1" in localrc
in the vm :
for i in {1..4} ; do swift-ring-builder /etc/swift/object.builder set_info --ip 127.0.0.${i} --change-ip node${i} --change-replication-ip node${i} -y; done
edit /etc/hosts accordingly (actually this doesn't change anything)
swift-ring-builder /etc/swift/object.builder write_ring
swift-init object start

The server tries to compare the hostname in the ring (https://github.com/openstack/swift/blob/master/swift/common/storage_policy.py#L76) with the ip addresses returned by whataremyips (https://github.com/openstack/swift/blob/master/swift/common/utils.py#L2602) without success, even if we want it to bind on every ("0.0.0.0") interfaces.
We are using swift v2.22.0, reproduced on master in saio