[review] dcbw/huawei-at-dhcp: use AT^DHCP response if available for NDISDUP-capable devices

[Dan Williams]

Hi,

I had at least one report of a HiSense device that had successful
AT^NDISSTATQRY reply but DHCP didn't work.  There's been discussion on
this in the past [1] with no real conclusion that I can see, but maybe
^DHCP works here instead.  So I just went ahead and did that.  It'll
need more testing with Huawei modems to make sure we can actually rely
on the results (we know we can't for QMI-based devices) but at least the
patch can be reviewed.

Dan

[1] http://lists.freedesktop.org/archives/modemmanager-devel/2014-October/001576.html