If a distro comparison update task fails (returning a non-zero value to
indicate as such) we were not able to see this easily from the frontend.
Show success/failure in the form of a label on the task page and general
update list/detail, and if the task fails while we're watching then make
the progress bar go red as well. Also make a distinction between the
process failing (retcode > 0) and being terminated (retcode < 0, e.g.
process was killed).
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>