Make the exploring of all luns supported by an HBA more of a tunable.

Make the exploring of all luns supported by an HBA more of a tunable.

If we're probing luns, and each probe succeeds, we keep going past
lun 7 if we're a SCSI3 or better device (until we fail to probe).

If we're probing luns, and a probe fails, we only keep going if
we're quirked *for* it (CAM_QUIRK_HILUNS), and if we're not quirked
*against* it (CAM_QUIRK_NOHILUNS), or we're a SCSI3 or better device
and the tunable (kern.cam.cam_srch_hi) is set non-zero.

Obtained-from: FreeBSD