SLING-6369 MissingElementsException should not hide any stack traces of contained exceptions

Rely on suppressed exceptions being introduced with Java7.

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1773229 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/pom.xml b/pom.xml
index 6a71b1a..a246518 100644
--- a/pom.xml
+++ b/pom.xml
@@ -52,6 +52,7 @@
         optionally using -Dmaven.surefire.debug to enable debugging.            
      -->
     <properties>
+        <sling.java.version>7</sling.java.version>
         <!-- Set this to run the server on a specific port
         <http.port></http.port>
          -->