This fixes regression in iproute2-3.5.1 when `ip addr show' skipped
interfaces without network layer address.

Wrong output:
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:50:54:00:0f:03 brd ff:ff:ff:ff:ff:ff
    inet 10.34.25.198/23 brd 10.34.25.255 scope global eth0
    inet6 2620:52:0:2219:250:54ff:fe00:f03/64 scope global dynamic
       valid_lft 2591919sec preferred_lft 604719sec
    inet6 fe80::250:54ff:fe00:f03/64 scope link
       valid_lft forever preferred_lft forever

Expected output:
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:50:54:00:0f:03 brd ff:ff:ff:ff:ff:ff
    inet 10.34.25.198/23 brd 10.34.25.255 scope global eth0
    inet6 2620:52:0:2219:250:54ff:fe00:f03/64 scope global dynamic
       valid_lft 2591896sec preferred_lft 604696sec
    inet6 fe80::250:54ff:fe00:f03/64 scope link
       valid_lft forever preferred_lft forever
5: veth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 8a:ec:35:34:1f:a8 brd ff:ff:ff:ff:ff:ff
6: veth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 2e:97:ef:77:40:82 brd ff:ff:ff:ff:ff:ff
Signed-off-by: Petr Písař <ppisar@redhat.com>