Add option to force removing Dockerfile.stfubuntu

docker/build.sh

@@ -5,9 +5,9 @@
 set -e
 set -vx
 
-if [ "$1" == "--force-stfubuntu"]
-then
-    doker rmi `docker images -q stfubuntu`
+# Force removing stfubuntu docker image
+if [ "$1" == "--force-stfubuntu" ]; then
+    doker rmi `docker images -q stfubuntu` || exit 1
 fi
 # Check and build stfubuntu image
 if [ -z `docker images -q stfubuntu` ]; then