In the scsi_debug driver, the virtual_gb option
ignores the sector_size, implicitly assuming
that is 512 bytes.
So if 'virtual_gb=1 sector_size=4096' the result is
an 8 GB (virtual) disk.

ChangeLog:
   - correct get_sdebug_capacity() calculation of
     sectors when virtual_gb option is used. Needs
     to take into account sector_size.

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>