scsi: scsi_debug: call resp_*() function after setting host_scribble

Error injection in scsi_debug (e.g. opts=16, SDEBUG_OPT_TRANSPORT_ERR)
currently doesn't work correctly because the test for sqcp in
resp_read_dt0() and similar resp_*() functions always fails.  sqcp is
set from cmnd->host_scribble, which is set in schedule_resp(), which is
called from scsi_debug_queuecommand() after calling the resp_* function.

Defer calling resp_*() until after cmnd->host_scribble is set in
schedule_resp().

Fixes: c4837394 "scsi_debug: add multiple queue support"
Signed-off-by: Martin Wilck <mwilck@suse.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>