fixup autoupdate for new build system
fixup autoupdate for new build system

- write board is to /etc/lsb-release
- send board id to omaha
- require board to find latest image

Review URL: http://codereview.chromium.org/633001

coreos/dev-util,marineam/coreos-dev-util,mgireesh05/dev-util,mgireesh05/dev-util,mgireesh05/dev-util,marineam/coreos-dev-util,coreos/dev-util,coreos/dev-util