Cast environment variables to integers

[cbkerr]

Description

Cast environment variables to integers in example code.

Motivation and context

Ran into the undefined operator error in Communicator where it checks the following with ranks_per_partition as a string.

if self.cpp_mpi_conf.getNRanksGlobal() % ranks_per_partition:

How has this been tested?

I changed the code I copied which fixed the problem. I didn't test the change for getting ACTION_THREADS_PER_PROCESS

Checklist:

• I have reviewed the Contributor Guidelines.
• I agree with the terms of the Row Contributor Agreement.
• My name is on the list of contributors (doc/src/contributors.md) in the pull request source branch.
• I have added a change log entry to doc/src/release-notes.md.

[joaander]

Yet another example showing that duck typing is an epic failure. I would also welcome a fix to HOOMD-blue that casts the RHS of that operator to int. Isaac found a similar case where hoomd.variant.box.InverseVolumeRamp should cast parameters before initializing the C++ struct.