fixup: Do not try to start Qemu for platform_rpi

ref #961
okl4 & priority.run: new order of core services

ref #961
fixup "hw: adjust expected serial start-message in run"

fix #963
fixup "hw: beautify scheduling-priority code"

re-add priority down-scaling

ref #960
fixup: cpu_session: fix semantic of scale_priority

fixup for commit 5a42f40f04981581327639a75298e9e653ef39f5
ref #961