[JUNIT] Added Testcases for ActivityHandler

Added some testcases to check whether the activities are directed to the
correct users with the correct activityType.

Change-Id: Ic475d66b11ca432885096bb6511a17f25c0a5707
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/849
Tested-by: Jenkins CI
Reviewed-by: Arsenij Solovjev <xeper000@gmail.com>
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>