docker: Fix install.

- Need a newer version of pip to install eris.
- Eris has new --config and --version options.
- Not adding --apt-install-tools because tools are already bundled
  in the docker image.

packaging/Dockerfile

@@ -4,6 +4,7 @@ FROM ubuntu:impish
 RUN apt-get update
 RUN DEBIAN_FRONTEND=noninteractive apt-get install -y tzdata
 RUN apt-get install -y sudo python3.9 python3-pip
+RUN python3.9 -m pip install --upgrade pip
 COPY . eris
 RUN cd eris && ./install