MFC r267547, r267551 (by trasz):
Add LUN-associated name to VPD, to make Hyper-V Failover Cluster happy.
MFC r267574 (by trasz):
Make cs_terminating a bool; no functional changes.
MFC r267610 (by trasz):
Rework session termination in iSCSI target to actually wait
for any outstanding commands to be properly aborted by CTL.
Without it, in some cases (such as files backing the LUNs
stored on failing disk drives), terminating a busy session
would result in panic.
MFC r267637:
Add iSCSI Target Name ID descriptor to VPD 83h.

It shall/should be there according to SPC-4, and istgt also provides it.
MFC r267641:
Add some more CTL_FLAG_ABORT check points.

This should allow to abort commands doing mostly disk I/O, such as VERIFY
or WRITE SAME.  Before this change CTL_FLAG_ABORT was only checked around
data moves, which for these commands may not happen for a very long time.
MFC r267648:
serial_num and device_id fields are not necessarily null-terminated.

Before this it was impossible to use all 16 bytes of serial number, and
client always got serial number NULL-terminated, that is not required.