Silence Maven complaining about unset versions of reporting plugins

Since we use the reporting plugins only in the parent pom.xml there's no
point in using the new pluginManagement tag in the reporting section
which was introduced to fix
https://issues.apache.org/jira/browse/MSITE-443

Change-Id: I750ca3765e95afb06609a362fb3354afc3b66b90
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

pom.xml

@@ -519,14 +519,17 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-jxr-plugin</artifactId>
+        <version>2.5</version>
       </plugin>
       <plugin>
         <groupId>org.codehaus.mojo</groupId>
         <artifactId>findbugs-maven-plugin</artifactId>
+        <version>3.0.0</version>
       </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-surefire-report-plugin</artifactId>
+        <version>2.18.1</version>
         <configuration>
           <aggregate>true</aggregate>
           <alwaysGenerateSurefireReport>false</alwaysGenerateSurefireReport>