common/scsi_debug: prepare scsi_debug in zoned mode

common/scsi_debug: prepare scsi_debug in zoned mode

To allow running tests using scsi_debug device with the zoned mode
disabled (current setup) as well as enabled, modify the _init_scsi_debug
helper function. When RUN_FOR_ZONED is set, specify zbc=host-managed
parameter to scsi_debug module so that the scsi_debug devices are
prepared in zoned mode.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>