Get rid of the installer registration concept

This is a legacy of the days where the kvm kernel modules would
be installed either by compiling the source code or via "kmod"
like packages, and the loading and unloading of kernel modules
would depend on that.

Nowadays, we can assume that the kvm modules always come from
the kernel packages.

One last piece of refiniment here would be to remove the module
loading/unloading feature from the base installer code.

Signed-off-by: Cleber Rosa <crosa@redhat.com>