tc_filter: make use of _parser for getting the relevant items

The previous patch introduced a lot of parsing methods for the new
qdisc tc module. This patch changes the already existing filter
module to use them.

Change-Id: I8fedf4b923288472aa4f45168d42601fe7c9c164
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/30466
Reviewed-by: Dan Kenigsberg <danken@redhat.com>