flimflam: Choose another ipconfig when one goes away

A connection is associated with an IPConfig.  Thus, when
we remove an IPConfig the associated connection is destroyed,
marking the service as disconnected as well.  If the device
still has alternate IPConfigs, we should try to launch one
of them.

BUG=chromium-os:29050
TEST=Manual:
Mark an Ethernet connection as static IP and ensure we
stay connected (actually we quickly bounce back to the CONFIGURING
state -- fixed in follow-on CL)

Change-Id: Ia46c82df5310200e89ce262440464d0b20d96341
Reviewed-on: https://gerrit.chromium.org/gerrit/20689
Commit-Ready: Paul Stewart <pstew@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>
3 files changed