[MINOR] move the load balancing algorithm to be->lbprm.algo

[MINOR] move the load balancing algorithm to be->lbprm.algo

The number of possible options for a proxy has already reached
32, which is the current limit due to the fact that they are
each represented as a bit in a 32-bit word.

It's possible to move the load balancing algorithms to another
place. It will also save some space for future algorithms.