Using released ONOS 2.5.7

Change-Id: I5bcbd966fa2b3b554e921f0ba4702d6ab1559dae
diff --git a/VERSION b/VERSION
index 7fc5a96..4ed678a 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-5.1.0-dev11
+5.1.0-dev12