LIO iSCSI Target for Windows Server 2016 Cluster disk - device is not ready
You might want to try clearing SCSI-3 Persistent Reservations as LIO could "forget" to update them after LUN ownership changed.
Clear-ClusterDiskReservation
I solved this issue. It appears that the version of LIO included in Fedora 22 does not correctly support the SCSI-3 Persistent Reservations. I switched to using scsi-target-utils and that worked without issue immediately with this config:
backing-store /blah/blah/blah/zvol initiator-address 172.16.20.0/24 incominguser hgx blahblahblah