fix k3s_storage_endpoint being null in k3s script

[sapher]

Hello,

This is a bug fix for when you are trying to use sqlite as the storage endpoint, the k3s_install.sh script fail because k3s_storage_endpoint is null.

Thank you

[Ticiano-mw]

Had the same problem

[drpebcak]

This repo is unmaintained, so there is unlikely to be a fix coming. I have a fork that I use, but I don't use sqlite, so this same problem most likely exists there.

[sapher]

@drpebcak that unfortunate :/