Updated CHANGELOG.md for release 1.51.2
Updated CHANGELOG.md for release 1.51.2

telstra/open-kilda,telstra/open-kilda,telstra/open-kilda,jonvestal/open-kilda,telstra/open-kilda,telstra/open-kilda,telstra/open-kilda,jonvestal/open-kilda,telstra/open-kilda,jonvestal/open-kilda,jonvestal/open-kilda,jonvestal/open-kilda