Movign to 2.5.7-rc2 and including DT FTTB workflow changes in sadis, olt, dhcpl2relay

Change-Id: Ic07c052c9803a839a23976977d33e58b28523d7c
diff --git a/Dockerfile.voltha-onos b/Dockerfile.voltha-onos
index 850bb4a..2ddb18d 100644
--- a/Dockerfile.voltha-onos
+++ b/Dockerfile.voltha-onos
@@ -34,7 +34,7 @@
 
 
 # Unpack and install specific apps from download stage
-FROM onosproject/onos:2.5.7-rc1 as install
+FROM onosproject/onos:2.5.7-rc2 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:2.5.7-rc1
+FROM onosproject/onos:2.5.7-rc2
 
 # The ENV settings must be replicated below as they are not shared between stages
 ENV ONOS=/root/onos