credit2: Refactor runqueue initialization

credit2: Refactor runqueue initialization

Several refactorizations:
* Add prv->initialized cpu mask
* Replace prv->runq_count with active_queue mask
* Replace rqd->cpu_min,cpu_mask with  active cpu mask
* Put locks in the runqueue structure, rather than borrowing the
existing cpu locks
* init() initializes all runqueues to NULL, inactive, and maps all
pcpus to runqueue -q
* alloc_pcpu() will add cpus to runqueues, "activating" the runqueue
if necessary.  All cpus are currently assigned to runqueue 0.

End-to-end behavior of the system should remain largely the same.

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>