Releasing 2.6.0 for voltha-system-tests

Change-Id: I8f4c2d11b01569b42eddc3aa7ac7f117b29156ca
diff --git a/VERSION b/VERSION
index 69fa968..e70b452 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.5.0-dev
+2.6.0