Fix ruby to load kernel modules

I could not get your code to run on my stock Ubuntu 12.10 machine.

With this change it'll do

Fixes: 
- remove unneeded inclusion of kernel_modules in ovswitch fact
- change back to "confine :linux", as the ":exists" confine did not fire. I could not find any code to support that confine. Did you use any dependency that you did not document (or which overlooked?)