Updating voltha-2.8 release, bumping to 2.10 and using master for all references

Change-Id: I5dbef01fb43f95eb5663963d61409ff07b59e2c3
diff --git a/VERSION b/VERSION
index dedcc7d..14377a8 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.9.1
+2.10.0-dev