[REFACTOR] Simplified if-constructs

The tool PMD pointed out some nested if-constructs that can be
simplified. This patch addresses three of them (and removes an unused
method parameter).

Change-Id: Ic80dbb368a04b2f0e4f0c8ae62b78eff66dd12c7
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1517
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>
Tested-by: Jenkins CI
Reviewed-by: Damla Durmaz <ddurmaz88@gmail.com>
Reviewed-by: Franz Zieris <zieris@inf.fu-berlin.de>