Test for repeatability

Update Docker container and run instructions to avoid MPI / Docker security conflicts

This approach is expedient for this example, but probably not the best approach for production deployments.  See separate discussion on this issue open-mpi/ompi#4948.

Dockerfile

@@ -1,4 +1,4 @@
-FROM library/python:3.9-slim-buster
+FROM library/python:3.9-slim-bullseye
 LABEL maintainer="Mark Forrer<mark.forrer@lbl.gov>"
 ENV PYTHONUNBUFFERED=1 LANG=C.UTF-8
 COPY Pipfile* /tmp/

README.md

@@ -62,7 +62,7 @@ This command runs a `bash` shell inside the Debian-based Docker container.  Pres
 back to the command prompt for the host OS.
 
 ```bash
-docker run -it --rm ptmcmc-example
+docker run -it --rm --cap-add=SYS_PTRACE ptmcmc-example
 ```
 
 
@@ -86,7 +86,7 @@ As above, launch (or use) a `bash` shell in a Docker container.  Press CRTL-D to
 container and return to the command prompt for the host OS.
 
 ```bash
-docker run -it --rm ptmcmc-example
+docker run -it --rm --cap-add=SYS_PTRACE ptmcmc-example
 ```
 
 For subsequent examples in this section, both example code and PTMCMCSampler code are run from the