netlink: re-route remaining messages after getting request

Ususally, a response of multiple messages goes with the flag NLM_F_MULTI.
But in some cases the kernel throws several messages with the same
sequence numbers, but without NLM_F_MULTI. We can not rely on a timeout,
so, route all except first one to the default queue, if it exists.

FIXME: file a bug on the kernel
netlink: mirror packets to queue 0
ipdb: fix ipaddr transaction
ipdb: interface as a context manager
ipdb: pop() for upset