Move ARGs to prevent invalidating docker caches

Having the ARG at the top of the dockerfiles
cause all the cached layers below to be invalidated
resulting in needlessly re-downloading or re-copying
files

Change-Id: Ie701b1556ee21ecdcf629e06c9b26d80af0fb344
diff --git a/docker/Dockerfile.ro_core b/docker/Dockerfile.ro_core
index 5b41c89..1fbabe0 100644
--- a/docker/Dockerfile.ro_core
+++ b/docker/Dockerfile.ro_core
@@ -17,13 +17,6 @@
 
 FROM golang:1.12-alpine3.9 AS build-env
 
-ARG org_label_schema_version=unknown
-ARG org_label_schema_vcs_url=unknown
-ARG org_label_schema_vcs_ref=unknown
-ARG org_label_schema_build_date=unknown
-ARG org_opencord_vcs_commit_date=unknown
-ARG org_opencord_vcs_dirty=unknown
-
 # Install required packages
 RUN apk add --no-cache wget git make build-base protobuf protobuf-dev
 
@@ -44,6 +37,13 @@
 # Copy files.
 COPY ro_core ./ro_core
 
+ARG org_label_schema_version=unknown
+ARG org_label_schema_vcs_url=unknown
+ARG org_label_schema_vcs_ref=unknown
+ARG org_label_schema_build_date=unknown
+ARG org_opencord_vcs_commit_date=unknown
+ARG org_opencord_vcs_dirty=unknown
+
 # Build
 RUN cd ro_core && go build -o /build/ro_core \
 	-ldflags \