Use wickedd-dhcp{6,4} for DHCP test (bnc#866617)

instead of (dropped) dhcpcd-test

Copied the test from an earlier port in a different package:
https://gitorious.org/opensuse/network-autoconfig/commit/4104e47b530834e3106b1cdc55375bf06eec6e79
Updated changelog
old testsuite: stating systemd services is no longer done

it was removed in
https://github.com/yast/yast-yast2/commit/6d6f8ec39d239e2c4645a786c244537c45fb18e5
Merge pull request #165 from yast/dhcpcd-test-iz-ded

Use wickedd-dhcp{6,4} for DHCP test (bnc#866617)