It's not immediately obvious what numeric values mean for CPU scheduling policy.
Let's document this and add doc reference.
Related: OS#4107
Change-Id: Ib047762a336851e6205d77c83068a99d8a868e8b
By default systemd will execute service with root directory
(or home directory for user instance) which might result in
attempts to create files in unexpected place. Let's set it
to 'osmocom' subdir of state directory
(/var/lib for system instance) instead.
Related: OS#4821
Change-Id: I4b7bcd441e5da81c4c5267715675041171a1ce1e