Fix undetected runtime dependency usage problem from previous commit

Fix undetected runtime dependency usage problem from previous commit

In module 'ajdoc', our tests need tools.jar when running on JDK 8 in
order to dynamically compile during runtime. Hence, dependency
com.github.olivergondza:maven-jdk-tools-wrapper was re-added to the POM
(with test scope this time) and Maven Dependency plugin configured to
regard it as a used dependency and not falsely report it as unused.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>