nwfilter: Tear down temp. filters when tearing all filters
    
    Refactor the ebiptablesTearNewRules function so that the teardown of temporary
    filters can also be called by the ebiptablesAllTeardown function.
    
    This fixes a problem that leaves temporary filters behind when a VM shuts down
    while its filters are modified.
    
    Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
    
    v1->v2:
      - test cases adjusted to expect more commands