Test apt addon with disallowed PPA when `sudo` is enabled
Test apt addon with disallowed PPA when `sudo` is enabled

This is actually a case we missed when we shipped
https://github.com/travis-ci/travis-build/pull/723
to production.

A disallowed PPA's are ends up causing a TypeError, since `String`
responds to `:[]`, but it can't take a Symbol as an argument.

andyli/travis-build,jhass/travis-build,craigcitro/travis-build,kevmoo/travis-build,jhass/travis-build,craigcitro/travis-build,akoeplinger/travis-build,andyli/travis-build,kevmoo/travis-build,JuliaCI/travis-build,JuliaCI/travis-build,akoeplinger/travis-build