systemd cgroup drivers should not delegate everything to fs drivers

[kolyshkin]

Currently, systemd cgroup drivers (both v1 and v2) set systemd unit parameters (for those parameters that systemd supports), and then unconditionally fall back to fs driver, setting all the parameters again by writing to corresponding cgroup files.

There should be no such duplication, i.e. cgroup drivers should fall back to fs drivers only for parameters which are not supported by systemd. Otherwise, some discrepancies may occur, for example, systemd interprets cpu period and cpu quota in a specific manner, and most probably the configuration it sets is immediately overwritten by fs[2] driver.

A way to achieve this is to "unset" (set to 0) configs.Cgroup parameters that are used / known to systemd (in genV{1,2}ResourcesProperties).

[kolyshkin]

Obsoleted by #4072