Fixed Workdir in Dockerfile.

Makefile

@@ -1,3 +1,4 @@
+all: benchmark statistics
 
 benchmark: docker/container.ok
 	docker container run --rm -it -v `(pwd)`:/benchmark/data convganbenchmark python3 /benchmark/data/run_all_exercises.py

docker/Dockerfile

@@ -10,4 +10,5 @@ COPY requirements.txt /benchmark/requirements.txt
 RUN pip install -r /benchmark/requirements.txt
 
 COPY run.sh /benchmark/run.sh
+WORKDIR /benchmark/data
 CMD /benchmark/run.sh