global-defaults: Clear global JDK version

Set global JDK version to empty

Change-Id: I1b4c9f5cfdf1e8e53041b2162579253d42a974a1
Signed-off-by: Jessica Wagantall <jwagantall@linuxfoundation.org>
diff --git a/jjb/global-defaults.yaml b/jjb/global-defaults.yaml
index 9dd302f..f865092 100644
--- a/jjb/global-defaults.yaml
+++ b/jjb/global-defaults.yaml
@@ -14,6 +14,9 @@
     # default gerrit server definition
     server-name: 'Primary'
 
+    # Java
+    jdk: ''
+
     # Maven
     onap-infra-mvn-opts: |
         --show-version