tests/scripts: Fix minikube script
tests/scripts: Fix minikube script

Default to virtualbox driver. `minikube config get vm-driver` does not
work when default is used.

Fixes #3208.

Signed-off-by: Kaushal M <6114cda83a9cffdec58aade10dbd71577eeec67d@gmail.com>

rook/nfs,rook/rook,rook/rook,rook/rook,rook/rook,rook/nfs,rook/rook,rook/nfs