add Lets encrypt staging certificate to cert store in test container

Dockerfile

@@ -23,6 +23,8 @@ RUN apk --no-cache add \
   rsync \
   rust
 
+COPY ./test/pytest/le-staging-bundle.pem /usr/local/share/ca-certificates/le-staging-bundle.pem
+RUN update-ca-certificates
 COPY ./requirements.txt /requirements.txt
 RUN pip install -r /requirements.txt
 RUN ln -s /usr/bin/python3 /usr/bin/python