Small TFTP fixes
Global cleanup of kopts.

Kopts are now logical, and consistent to deal with.
* $kopts_installer is used for the installer
* $kopts_installed is used for the installed machine
* $kopts is added to both of the above variables.
* You can use all the options together. Duplicates are removed.

This makes more sense because you now clearly know which kopts is which,
and since in most cases you're adding the option to both installed and
installer, the default $kopts does just that.