fix failing test to use kill instead of stop

TestCreateStartRestartStopStartKillRm was failing because stop has been
changed to not kill containers.

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Merge pull request #4782 from unclejack/fix_TestCreateStartRestartStopStartKillRm

fix failing test to use kill instead of stop