This patch fixes an issue where alpha releases were distributed in the beta and release channels for Ubuntu and Debian distributions. Alpha releases are now distributed only in the development channel. Test-Information: Tested the patch on Debian Stretch by creating a new repository using update_debian_repo.sh and importing builds that were built for Debian Stretch on 4.0beta2, 4.0rc6, 4.0, 5.0alpha and 5.1alpha tags, and some development builds (5.0alpha-dev8). 5.1alpha tag was created locally to have an alpha build that contained the fix. Tested importing builds in the order that originally caused the issue (4.0rc6 then 4.0 then 5.0alphaX) before and after the fix. Change-Id: I65f3d188872112e1d770e6a6af0814d44fcd4bba