hyperv/storvsc: Fix the blkvsc disk attachment issues.

• The original 'disengage' ATA controller model does not work properly for all possible disk configurations. Use the newly added ATA disk veto eventhandler to fit into all possible disk configuration.
• If the 'invalid LUN' happens on blkvsc controllers, return CAM_DEV_NOT_THERE so that CAM will not destroy attached disks under the blkvsc controllers.

Submitted by: Hongjiang Zhang <honzhan microsoft com>
Discussed with: mav
MFC after: 1 week
Sponsored by: Microsoft
Differential Revision: https://reviews.freebsd.org/D7693