credit: recalculate per-cpupool credits when updating timeslice

credit: recalculate per-cpupool credits when updating timeslice

When modifying the timeslice of the credit scheduler in a cpupool the
cpupool global credit value (n_cpus * credits_per_tslice) isn't
recalculated. This will lead to wrong scheduling decisions later.

Do the recalculation when updating the timeslice.

Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Alan.Robinson <alan.robinson@ts.fujitsu.com>
Reviewed-by: Dario Faggioli <dario.faggioli@citrix.com>