weed server: mkdir first

docker/Dockerfile.go_build

@@ -16,11 +16,12 @@ EXPOSE 9333
 # s3 server http port
 EXPOSE 8333
 
+RUN mkdir -p /data/filerdb
+
 VOLUME /data
 
 RUN mkdir -p /etc/seaweedfs
 RUN cp /go/src/github.com/chrislusf/seaweedfs/docker/filer.toml /etc/seaweedfs/filer.toml
-RUN mkdir -p /data/filerdb
 RUN cp /go/src/github.com/chrislusf/seaweedfs/docker/entrypoint.sh /entrypoint.sh
 RUN chmod +x /entrypoint.sh
 RUN cp /go/bin/weed /usr/bin/