MFC r346491: Polish SCSI sense data validity checks.

According to specs and common sense, all sense data reported in descriptor
format should be valid. But practice shows different, some devices return
descriptors with invalid data, resulting in error messages looking worse.

Decouple block/stream commands sense data and information field printing.
Looking on present specs, there are much more cases when those fields are
not related, and incomplete old code was not printing valid sense data and
leaving empty lines for invalid.