Comment 2 for bug 1421037

Reviewed: https://review.openstack.org/156198
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=c3b7f1b2ae7af995f4815e3571c9828683dc0db7
Submitter: Jenkins
Branch: master

commit c3b7f1b2ae7af995f4815e3571c9828683dc0db7
Author: Fei Long Wang <email address hidden>
Date: Tue Feb 17 00:58:45 2015 +1300

    Fix metering agent failure when chain missing

    The metering agent will fail if one of the iptables chains
    is missing, which will cause errors extracting data from
    all the other chains. Add a simple try/except to let the
    loop continue.

    Closes-Bug: #1421037

    Change-Id: I370ee0e2cc58ca7e1c5ef9bf4dbcce5abf7545a1