Building voltha-onos off ONOS:2.2.2-rc6

Change-Id: I17de59a5a41da98fdc6d8e4ef2f2fb8c551bfe62
diff --git a/Dockerfile.voltha-onos b/Dockerfile.voltha-onos
index 941226b..b901992 100644
--- a/Dockerfile.voltha-onos
+++ b/Dockerfile.voltha-onos
@@ -34,7 +34,7 @@
 
 
 # Unpack and install specific apps from download stage
-FROM onosproject/onos:2.2-latest as install
+FROM onosproject/onos:2.2.2-rc6 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:2.2-latest
+FROM onosproject/onos:2.2.2-rc6
 
 # The ENV settings must be replicated below as they are not shared between stages
 ENV ONOS=/root/onos