device: fix wrongly considering ipv6.may-fail for ipv4

Fixes: 5e71f016 ('device: merge stage3 and stage4 ip-config function for IPv4 and IPv6')
(cherry picked from commit a0179362)
(cherry picked from commit 0adfcadc)
(cherry picked from commit 1438d5a9)
(cherry picked from commit 584f467e)
(cherry picked from commit a6490db9)
17 jobs for nm-1-18 in 55 minutes and 1 second (queued for 44 seconds)
Status Job ID Name Coverage
  Test
passed #4466942
checkpatch

00:01:40

manual #4466949
allowed to fail manual
t_centos:7.5.1804
manual #4466950
allowed to fail manual
t_centos:7.6.1810
manual #4466956
allowed to fail manual
t_debian:10
manual #4466955
allowed to fail manual
t_debian:9
manual #4466958
allowed to fail manual
t_debian:sid
manual #4466957
allowed to fail manual
t_debian:testing
manual #4466943
allowed to fail manual
t_fedora:28
manual #4466944
allowed to fail manual
t_fedora:29
manual #4466945
allowed to fail manual
t_fedora:30
passed #4466946
t_fedora:31

00:53:29

manual #4466947
allowed to fail manual
t_fedora:32
manual #4466948
allowed to fail manual
t_fedora:rawhide
manual #4466951
allowed to fail manual
t_ubuntu:16.04
manual #4466952
allowed to fail manual
t_ubuntu:18.04
manual #4466954
allowed to fail manual
t_ubuntu:devel
manual #4466953
allowed to fail manual
t_ubuntu:rolling