Sourcing envDefaults in onos-prepare-release

Change-Id: I43479a35ff5fa5a57647355b13989ac5c733d5f5
diff --git a/tools/build/onos-prepare-release b/tools/build/onos-prepare-release
index 658151d..b174738 100755
--- a/tools/build/onos-prepare-release
+++ b/tools/build/onos-prepare-release
@@ -29,5 +29,6 @@
 git tag -l | grep -q $ONOS_VERSION && { echo "ERROR: Version already exists"; exit -1; }
 
 export ONOS_ROOT=$DIR
+. $ONOS_ROOT/tools/build/envDefaults
 exec bash -i