In GEOM debugging output, show consumer for cloned and duplicated bio's.

When using bio's created by g_clone_bio() or g_duplicate_bio()
their consumer device (the device to which their I/O requests
are sent) is listed by the geom debugging facility as [unknown].
If available, this update lists the consumer associated with
the bio's parent.

MFC after: 2 weeks
Sponsored by: Netflix