Stop lb-docker-run requesting sudo for unprivileged user

If using docker --user then the entrypoint shouldn't be doing anything that requires sudo. It doesn't seem (from my ignorant perspective) that it's normally necessary for the user to own their home directory, so I stopped the sudo chown command that tried to effect that.

Also, it doesn't seem possible that $HOME will ever need to be created, because the Dockerfile already creates /userhome, so I removed the sudo mkdir $HOME stuff too.

This is nice because now you can run lb-docker-run without needing to run as sudo.

I'm sure I've missed a reason why this was originally inserted, so I'm expecting @clemenci or @cburr to correct me 😄