dracut.cmdline says, that if the root= parameter does not include the server
for NFS root, the bootserver given by DHCP is used.

This doesn't work with wicked, as the lease file is never read in the right
place.
PoC fix:
https://build.opensuse.org/package/view_file/home:favogt:nfsroot/dracut/fix-bootserver.patch?expand=1

It should probably be fixed in a more general way though, as there are more
places where /tmp/net.$1.override is read, but /tmp/leaseinfo.$1.dhcp.* isn't.

To reproduce the issue, build an initrd image with nfs support and supply
"ip=dhcp rd.neednet=1 root=nfs4:/foo" as cmdline.