We already got a global function called id_generate() to create unique
IDs within QEMU. Let's use it in the network subsytem, too, instead of
inventing our own ID scheme here.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20210215090225.1046239-1-thuth@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>