SLING-3813 - Pax-Exam tests fail when executed under Java 8

Downgrade pax-exam version to 3.5.0 to ensure that tests can be executed
with Java 6.

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1615344 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/pom.xml b/pom.xml
index a0886c1..8adc981 100644
--- a/pom.xml
+++ b/pom.xml
@@ -48,7 +48,7 @@
     <slf4j.version>1.6.4</slf4j.version>
     <logback.version>1.1.2</logback.version>
     <sling.java.version>6</sling.java.version>
-    <pax-exam.version>4.1.0</pax-exam.version>
+    <pax-exam.version>3.5.0</pax-exam.version>
 
     <bundle.build.dir>
       ${basedir}/target