Fix cooker log download button

* Retrieve a build's log file location directly from the file system, as the one which is available at the time of the BuildStarted event is incorrect.

* Hide the "Download build log" button for builds which fail early (e.g. due to recipe parsing) and consequently have no cooker_log_path.

The following changes since commit 34399e5950509ffe978d9e6a31e91193d1bdcf0a:

toaster: orm Machines filter don't pass self in as parameter (2015-10-06 20:08:50 -0700)

are available in the git repository at:

git://git.yoctoproject.org/poky-contrib ed/toaster/submit/elliot/toaster/wrong_log-8373
http://git.yoctoproject.org/cgit.cgi/poky-contrib/log/?h=ed/toaster/submit/elliot/toaster/wrong_log-8373

Elliot Smith (2):
toaster: Manually retrieve log file location from filesystem
toaster: Hide "Download build log" button if log doesn't exist

 bitbake/lib/bb/ui/toasterui.py                     | 31 +++++++++++++++++++++-
 .../toastergui/templates/builddashboard.html       |  4 ++-
 2 files changed, 33 insertions(+), 2 deletions(-)

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Ed