- kernel-obs-build: change systemd's configuration to not to
TasksAccounting and not set a Maximum count of Tasks (boo#965564)

Please guide in getting this workaround / fix included into the package.
Not sure if this pkg source is the right point to do it.

The problem at hand: kernel-obs-build produces an initrd, which includes
systemd, currently version 228. Since version 226, the 'init' process
gets a fork-bomb protection (TasksMax=512 per default on init.scope)

While building inside OBS, we use the initrd produced by kernel-obs-build,
but then don't really use systemd to control any services. Just the start
of initrd already sets up cgroups and the entire build process is contained
within the init.scope cgroup in the end.

A solution which worked (tested) is the provided one: kernel-obs-build receives
a special systemd configuration, disabling the Task Accounting. This is only used
in the initrd produced by kernel-obs-build, thus will not impact users directly