Set a default value for JAVA_HOME

Change-Id: If5f036f0294cd20b06ad83761e459a9ab75356a9
diff --git a/jjb/onos/onos-run-stc.sh b/jjb/onos/onos-run-stc.sh
index 393e524..e413f64 100644
--- a/jjb/onos/onos-run-stc.sh
+++ b/jjb/onos/onos-run-stc.sh
@@ -8,6 +8,7 @@
 . tools/build/envDefaults
 
 # initialize development environment for STC
+export JAVA_HOME=
 . tools/dev/bash_profile