Fix ovn-rally cleanup task
Fix ovn-rally cleanup task

If deployer user is root, we do not need to remove the user

Signed-off-by: Hui Kang <06099befa36bf5a07a5196d8e1177abdf1d958ba@us.ibm.com>

sivakom/ovn-scale-test,openvswitch/ovn-scale-test,sivakom/ovn-scale-test,openvswitch/ovn-scale-test