Releasing official voltha-onos for 2.9 with ONOS 2.5.5

Change-Id: I3c6d941f242cf5a09b1194cc46b453b19f03d085
diff --git a/Dockerfile.voltha-onos b/Dockerfile.voltha-onos
index dbd2c0b..94d8c1f 100644
--- a/Dockerfile.voltha-onos
+++ b/Dockerfile.voltha-onos
@@ -34,7 +34,7 @@
 
 
 # Unpack and install specific apps from download stage
-FROM onosproject/onos:2.5-latest as install
+FROM onosproject/onos:2.5.5 as install
 
 # The ENV settings must be replicated below as they are not shared between stages
 ENV ONOS=/root/onos
@@ -58,7 +58,7 @@
 
 
 # Create the final image coping over the installed applications from the install stage
-FROM onosproject/onos:2.5-latest
+FROM onosproject/onos:2.5.5
 
 # The ENV settings must be replicated below as they are not shared between stages
 ENV ONOS=/root/onos