Docker: Update buildscript not to delete old images

Signed-off-by: Christian Franke <chris@opensourcerouting.org>

tests/topotests/docker/docker.sh

@@ -30,20 +30,7 @@ CDIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 # Script begin
 #
 
-OLD_IMAGE_SHA=$( \
-	docker images | \
-	egrep "^topotests" | \
-	sed -r "s/( )+/ /g" | \
-	cut -d " " -f 3 \
-)
-
-docker build --force-rm --pull --compress -t topotests . || \
-	log_fatal "failed to generate topotest docker image"
-
-if [ ! -z "$OLD_IMAGE_SHA" ]; then
-	log_info "Removing old topotest image"
-	docker rmi $OLD_IMAGE_SHA || \
-		log_warning "failed to remove old image"
-fi
-
-exit 0
+exec docker build --pull \
+		  --compress \
+		  -t frrrouting/topotests \
+		  .