interfaces using dhcp ipam.
Vendor latest dhcp4server, dhcp4client, dhcp4
Added additional tests for new functionality in dhcp2_test.go
Wrap d2g dhcp4client calls with our own which add clientID to packet.
Recent CNI specification changes require the container ID on ADD/DEL,
which the testcases were not providing. Fix that up so things work
when this repo gets CNI revendored.
Namespace creation had an unergonomic interface and isn't used, except
for testing code. Remove it; downstream users should really be creating
their own namespaces
