The input of the testEncodeInstance test was not adherent to the actual format
of the Ganeti configuration file: kvm has no HV_BLOCKDEV_PREFIX, and "hvparams"
inside an instance should only contain the values of the hypervisor parameters,
not the hypervisor name, which is already declared in the "hypervisor" field,
and which was not correctly aligned with the parameters in the "hvparams"
section.

All these problems are now fixed, and the assertions are changed accordingly.

Signed-off-by: Michele Tartara <mtartara@google.com>
Reviewed-by: Helga Velroyen <helgav@google.com>