[rancid] force10 support

[john heasley]

I'm considering not supporting SFTOS, the pre-FTOS O/S for Force10.  SFTOS
is EOL and AFAICT FTOS is supported on all of the hardware.  The differences
are slight but annoying enough and I'm not convinced its worth the effort.
For some that means upgrading, which may not be easy for them.

Who can honestly say that they can't upgrade and really need SFTOS support?