We need to add delegate yes to docker's service file so that it can
manage the cgroups of the processes that it launches without systemd
interfering with them and moving the processes after it is reloaded.

```
Delegate=
Turns on delegation of further resource control partitioning to
processes of the unit. For unprivileged services (i.e. those
using the User= setting), this allows processes to create a
subhierarchy beneath its control group path. For privileged
services and scopes, this ensures the processes will have all
control group controllers enabled.
```

This is the proper fix for issue #20152

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>