Duplicate config[:env] before running `#delete_if`
Duplicate config[:env] before running `#delete_if`

So that we don't delete secure variables

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