Building test distributable if it is not available already.

Change-Id: I39bd113da99143c2073e51306a3afad936dd53ce
diff --git a/tools/test/bin/proxy-stc b/tools/test/bin/proxy-stc
index 63e65cc..689dadd 100755
--- a/tools/test/bin/proxy-stc
+++ b/tools/test/bin/proxy-stc
@@ -6,6 +6,8 @@
 
 . $ONOS_ROOT/tools/build/envDefaults
 
+[ -f $ONOS_TEST_TAR ] || onos-package-test
+
 onos-push-test-bits $OCN
 onos-push-bits $OCN