=pro #3552 Upgrade ScalaTest to 1.9.2-SNAP2 for dbuild

* This can't go into 2.2.x since ScalaTest 1.9.2-SNAP2 has source incompatible changes and the dependecy in akka-multi-node-node-testkit would force people to upgrade.
Merge pull request #1650 from akka/wip-3552-upgrade-scalatest-for-dbuild-ban

=pro #3552 Upgrade ScalaTest to 1.9.2-SNAP2 for dbuild