Bump timeout in interactive tests from 10s -> 30s.

Seeing too many of these failures on our build servers.

https://scala-webapps.epfl.ch/jenkins/view/2.N.x/job/scala-nightly-auxjvm-2.11.x/148/jdk=jdk8,label=auxjvm/console

This is most likely due to load on the machines.
Merge pull request #4007 from retronym/topic/bump-timeout

Bump timeout in interactive tests from 10s -> 30s.