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
On ADD save the host device's name into its IFLA_ALIAS property and
rename the device to the requested CNI_IFNAME inside the container
to conform to the CNI specification. On DEL rename the device to
the original name and move it back into the host namespace.
