Comment 1 for bug 1045248

The line of code you reference was added in this commit, which isn't specific to adding the gateway fallback:

commit 345439f86a9ac8bd95cc7f382a3890d86f794b62
Author: Trey Morris <email address hidden>
Date: Fri Mar 30 10:14:08 2012 -0500

    update xen to use network_model

    blueprint xenapi-network-info-model

    updated xenapi to use the new network info models

    also:
    updated virt firewall to handle both old version and new hotness
    made a few minor changes to the network info model
    moved the legacy converstion shim from compute/utils to the model itself
    wharrgarbl'd a few of the tests

    NOTE: no unittests were skipped during the creation of this patch

    Change-Id: Ib77dd2bf4f0a525b73800441f19013e842c77f98

The fallback does seem kind of odd to me at first glance, but I haven't dug into in great detail. I'll confirm the bug since this does seem worth looking into and determining whether it is really desirable.