dhcp6: fixed to allow status option without message
dhcp6: temporally guarded release without config
dhcp6: initial --test <ifname> run implementation (fate#316111)
dhcp4: initial --test <ifname> run implementation (fate#316111)
socket: no sockets left is not always an error

Lowered error message to debug and changed to return 1
instead of a -1 error, as no sockets left can also mean,
we're done with them and there is no further timer set.
dhcp: adopted test run to new socket_wait code