* bonzini/nbd-next:
nbd: obey FUA on reads
nbd: do not include block_int.h
nbd: do not block in nbd_wr_sync if no data at all is available
nbd: consistently return negative errno values
nbd: consistently check for <0 or >=0
nbd: consistently use ssize_t
nbd: avoid out of bounds access to recv_coroutine array