Fix environment in singularity

• Make sure we get rid of extraneous shell variables set by users, and don't reload the user's bashrc.
• Add test to make sure the tutorial works in this style of environment

containers/jug/Dockerfile.dev

@@ -234,7 +234,7 @@ RUN echo "" >> /etc/jug_info                                            \
 
 ## make sure we have the entrypoints setup correctly
 ENTRYPOINT ["/usr/local/sbin/entrypoint.sh"]
-CMD ["bash", "--rcfile", "/etc/profile", "-l"]
+CMD ["bash", "--rcfile", "/etc/profile"]
 USER 0
 WORKDIR /
 SHELL ["/usr/local/bin/eic-shell"]