fix: remove container after generating protoc (#1306)

Add '--rm' option to docker command, so container will be removed
automatically. Otherwise we'll have many exited but not removed
containers as we run 'make protoc'.

Signed-off-by: Eryu Guan <eguan@linux.alibaba.com>

hack/protoc.sh

@@ -9,7 +9,7 @@ proto_modules="base cdnsystem dfdaemon manager scheduler"
 echo "generate protos..."
 
 for module in ${proto_modules}; do
-  if docker run -v $PWD:/defs ${PROTOC_ALL_IMAGE} \
+  if docker run --rm -v $PWD:/defs ${PROTOC_ALL_IMAGE} \
     -d ${PROTO_PATH}/$module -i . \
     -l ${LANGUAGE} -o . \
     --go-source-relative \