Reduce some more code duplication and split code

The Qlang module defines ResultStatus, but it was already defined in
Ganeti/Luxi.hs; let's remove the duplicate definition from there since
the proper place is in the newer module.

Also, in order to ease testing, we split some confd functions into a
separate module; this can be imported easily into QC for testing.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Agata Murawska <agatamurawska@google.com>