fix TestPause/serial/* tests for docker driver with containerd runtime

[ilya-zuyev]

These three failures seem related:

https://storage.googleapis.com/minikube-builds/logs/master/c31bd57/Docker_Linux_containerd.html#fail_TestPause%2fserial%2fPause
https://storage.googleapis.com/minikube-builds/logs/master/c31bd57/Docker_Linux_containerd.html#fail_TestPause%2fserial%2fPauseAgain
https://storage.googleapis.com/minikube-builds/logs/master/c31bd57/Docker_Linux_containerd.html#fail_TestPause%2fserial%2fVerifyStatus

Full log: https://storage.googleapis.com/minikube-builds/logs/master/c31bd57/Docker_Linux_containerdout.txt

[medyagh]

how about we stop the containers before we delete minikube so it doesnt hang