[opensuse-buildservice] frontend does too much when uploading a file

Hi, during a file upload the frontend performs superfluous (IMHO) tasks like sending the package metadata (which doesn't change during the upload) to the backend etc. The problematic method is "update_timestamp" in the Package() class (see models/package.rb). Instead of simply updating some timestamp tables it regenerates the complete metadata. I attached a small patch which _only_ updates the timestamp without touching any metadata. Btw. with this patch we gain a small perfomance boost: - executing the old version takes around 2.81 seconds - executing the new version takes around 1 second (measured with ruby's 'profiler' module) Marcus Ps. I don't know if this is a good "ruby style" but it works for me:)