toaster: builds pages Fix the download cooker log link

toaster: builds pages Fix the download cooker log link

The 'all builds' page was missing the download icon next to the outcome
icon, which allows you to download a build log from the 'all builds' page.

This patch brings it back. It also adds a check in the project builds page
to make sure the download icon only appears if the build generates a cooker
log, since builds that fail at the build request stage do not generate a
cooker log.

Signed-off-by: Belen Barros Pena <belen.barros.pena@intel.com>
Signed-off-by: Michael Wood <michael.g.wood@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>