systemctl called LoadUnit, GetUnit, GetAll in this order to get the properties.
It is useless to load units explicitly, because it won't ensure anything. The
unit may be freed immediately by the garbage collector.
It is unnecessary to call GetUnit, because systemctl can easily translate the
unit name to DBus path by itself.
GetAll will load the unit if necessary.
In some cases the main/control PID of a service can be outside of the
services cgroups (for example, if logind readjusts the processes'
cgroup). In order to clarify this for the user show the main/control PID
in the cgroup tree nonetheless, but mark them specially.