Suggest to add --dir when re-start install after cleanup

[Jia Liu]

In troubleshooting doc [1], when users hit an error during the first try and have to cleanup the whole cluster. It's better to re-start the installation with a new directory or "rm -rf "the asset directory when first try in case some dirty files influence the new install against current directory directly.

Finally, re-start the install process
./openshift-install create cluster

More reference is here[2].

Note that you almost certainly also want to clean up the installer state files too, including auth/,
terraform.tfstate, etc. The best thing to do is always pass the --dir argument to install and destroy.
And if you want to reinstall from scratch, rm -rf the asset directory beforehand.

[1] https://github.com/openshift/training/blob/master/docs/06-troubleshooting.md
[2] https://github.com/openshift/installer/#cleanup