Don't modify existing airgap k3s-install script (#372)

* Check for existing k3s install script during airgap deployment

Signed-off-by: Derek Nola <derek.nola@suse.com>

* Update vagrant file to newer OS

Signed-off-by: Derek Nola <derek.nola@suse.com>

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Signed-off-by: Derek Nola <derek.nola@suse.com>