Update jenkins version to 2.138.4.
</developers>
<properties>
-<!-- <jenkins.version>2.60.3</jenkins.version>-->
- <!--TODO before PR and MERGE: determine version!-->
+ <jenkins.version>2.138.4</jenkins.version>
<maven-surefire-report-plugin.version>2.20</maven-surefire-report-plugin.version>
<maven-hpi-plugin.injectedTestName>InjectedIT</maven-hpi-plugin.injectedTestName>
<maven-checkstyle-plugin.version>2.17</maven-checkstyle-plugin.version>
