manager: don't recalculate dynamic priorities too often
manager: don't recalculate dynamic priorities too often

Recalculating dynamic priorities requires deserializing all programs,
and that is slow. So do it at most once per 30 mins and don't hold
the mutex during prio calculation.

hyz0906/syzkaller,dotweiba/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,dotweiba/syzkaller,google/syzkaller,dotweiba/syzkaller,google/syzkaller,hyz0906/syzkaller,google/syzkaller,zoulasc/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,hyz0906/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,zoulasc/syzkaller,dotweiba/syzkaller,hyz0906/syzkaller,zoulasc/syzkaller,zoulasc/syzkaller,hyz0906/syzkaller