RAPI: move to nic parameters

In query we ask for nic.links, rather than nic.bridges
In create we accept both "link" and "bridge" and let the opcode deal
with it. Note that we still can create only one nic per instance.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>