Op/LUCreateInstance support for (no) name checks

This adds a new opcode parameter ‘name_check’ (similar to ip_check) that
is not required to be present (to easy backwards compatibility for
tools).

It also adds a CheckArguments to LUCreateInstance and changes the
workflow related to instance IP checks and NIC initialisation based on
it.

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