sort filenames
remove bogus @silent instance var

doesn't seem it had been used before i started working on this
https://github.com/travis-ci/travis-build/blob/8b0479f44b831b0f490434927cba6914266c1a98/lib/travis/build/script/addons/deploy.rb#L31
apparently it's really installt
actually neither travis-worker nor travis-build/app pass options
add specs for Addon::Deploy::Conditions, and fix wrong failure message for on: { tags: false }