VOL-3777: Disable ONU and OLT failing sometimes at VOLTHA - stale devices exist even after delete

- re-org the code to free up 'lockDevice' lock as soon as possible. The DeleteDevice RPC handler
  was held up on waiting for 'lockDevice' lock to be freed up in 'doStateDown'
  handler which potentially caused 'DeleteDevice' RPC to timeout and stale device
  was left in voltha.

Change-Id: I0fd5350dcde239f595b8e0b11a7a8e2466edeb9b
diff --git a/VERSION b/VERSION
index ff365e0..8188357 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-3.1.3
+3.1.4-dev