Build: fix maven.build.timestamp.format for releases

Change-Id: I7bab3c84f299d14a846763717542b1aff299d1ab
Reviewed-on: https://git.eclipse.org/r/48126
Reviewed-by: Judith Gull <jgu@bsiag.com>
Tested-by: Judith Gull <jgu@bsiag.com>
diff --git a/pom.xml b/pom.xml
index 0797c6f..548d12a 100644
--- a/pom.xml
+++ b/pom.xml
@@ -115,6 +115,7 @@
       <id>prepare-release</id>
       <properties>
         <milestone.version>I</milestone.version>
+        <maven.build.timestamp.format>yyyyMMdd-HHmm</maven.build.timestamp.format>
         <newVersion>${scout.base.version}.${maven.build.timestamp}-${milestone.version}</newVersion>
       </properties>
       <activation>