[Libguestfs] [PATCH libnbd v2 0/6] Test connection states.

Patch 1/6 was posted before and I didn't change it: https://www.redhat.com/archives/libguestfs/2019-May/thread.html#00134 That doesn't necessarily mean I shouldn't change it, I'm posting it again because the other patches depend on it. The main change in this series is we add three new API functions: nbd_aio_is_created - connection has just been created nbd_aio_is_connecting - is connecting or handshaking / option negotiation nbd_aio_is_processing - is issuing or receiving a reply Also in this change I used nbd_aio_is_connecting to simplify the handling of synchronous connects. Rich.