Document the -y option as a unit test option.
Add missing -v (and -y) to the usage message.

Requested by: eadler@
Remove targ_enable()/targ_disable() frontend methods.

Those methods were never implemented, and I believe that their concept is
wrong, since single frontend (SCSI port) can not handle several targets.
Separate concepts of frontend and port.

Before iSCSI implementation CTL had no knowledge about frontend drivers,
it had only frontends, which really were ports (alike to LUNs, if comparing
to backends).  But iSCSI added there ioctl() method, which does not belong
to frontend as a port, but belongs to a frontend driver.
Create separate iSCSI port for every target (and potentially portal group).
Burry devid port method, which was a gross hack.

Instead allow ports to provide wanted target port and target IDs, and
LUNs provide wanted LUN IDs.  After that core Device ID VPD code only
had to link them together and add relative port and port group numbers.
Make REPORT TARGET PORT GROUPS to return something more sensible.

It requires more formalized LUN mapping to be exactly correct.
Add support for SCSI Ports VPD page.

Ports should also be filtered by LUN mapping.
Do not set port wwnn/wwpn directly, call ctl_port_set_wwns() to update
also target_devid/port_devid respectively.
Change ctl_add_initiator()/ctl_remove_initiator() KPI.

 - Store data in struct ctl_port to make it dynamic;
 - Make ctl_add_initiator() to choose free iid if caller passed < 0;
 - Remove unneeded now pool of iids from iSCSI.
Add support for READ FULL STATUS action of PERSISTENT RESERVE IN.

So far without initiator IDs.
Pass through iSCSI session ISID from LOGIN request to the CTL frontend.

ISID is an important part of initiator transport ID for iSCSI.
Add initiator transport IDs to READ FULL STATUS.

This is a hack. Should be rewritten somehow to store full IDs, but still
not consume 512KB of RAM per target.