Target enumeration now uses separate poller to receive virtio
response messages. A special virtio_scsi_scan_base struct has
been added to keep track of how many targets we still have to
receive response from.
Making target scan async allows other pollers to run while
bdev_virtio still has to wait for a response.
Change-Id: Ia9af9d61fb4f880d0535df0b18aa443fff6dc9be
Signed-off-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/375132
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>