retry the atc js tests up to 3 times
retry the atc js tests up to 3 times

There's a bug in the Haskell TLS library that sometimes causes the SSL
negotiation to fail when downloading Elm packages. Normally we'd like to
fix this there but this is a good chance to dog-food our attempts
option.

zachgersh/concourse,cjcjameson/concourse,cjcjameson/concourse,zachgersh/concourse,cjcjameson/concourse,concourse/concourse,concourse/concourse,concourse/concourse,zachgersh/concourse,concourse/concourse,concourse/concourse