[PATCH] Fallback director

[Rogier R. Mulhuijzen]

Hi,

The whole director stacking thing came out of wanting to implement a 
"priority director", where instead of weight, you could give priority 
value for each backend. I had the idea of balancing over all backends with 
the same priority, but then ran into how that should be done. Stacking 
made it easy, just one backend per priority level, but then one doesn't 
really need a value, just a list of backends which is checked in order.

And since the Round Robin Director really only needed a minute change for 
that logic, I folded the Fallback Director into its code:

https://github.com/drwilco/varnish-cache/compare/director-stacking...fallback-director

Cheers,

 	Doc