Use "systemctl disable" instead of "service docker stop" refs #19439

Use "systemctl disable" instead of "service docker stop" refs #19439

"service docker stop" stops the daemon but it can be restarted from
prematurely by socket activation.  Whoops!

We need to use "systemctl disable" it so that it doesn't wake up
during the scratch space surgery on the /tmp directory.

Arvados-DCO-1.1-Signed-off-by: Peter Amstutz <peter.amstutz@curii.com>