Bugfix: TypeError when using configNetwork.addNetwork with bootproto as kw param.

A TypeError is raised when using configNetwork.addNetwork by providing
bootproto as a keyword argument, this patch solve this issue without
altering addNetwork and objectivizeNetwork interfaces.

Change-Id: I990286a8d834df7de1198e4f71057aa6e3bc2bcd
Signed-off-by: Giuseppe Vallarelli <gvallare@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/15423
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Sandro Bonazzola <sbonazzo@redhat.com>
Tested-by: Sandro Bonazzola <sbonazzo@redhat.com>