Issue in DHCP tests, that not all IP addresses are assigned

In tests/network/test_dhcp.py::TestIPv4Addresses::test_dhcp_static_leases is failing. But when stopped all IP addresses are assigned (or at least last time I checked).

• there may be something like wait4network added for each client, after udhcpc restart.

There are also problems with asserts before the final assert (the messages are wrong) and that they sometimes fail.