Clean up the sample flask app and PEP8ify the code to standards

[nnja]

Made a few updates:

• General code clean up
• Updated variable names to conform to Python standards
• PEP8ified the code

If the changes look good, the tags will need to be updated to reflect the steps in the associated tutorial.

Includes changes to the corresponding tutorial via MicrosoftDocs/azure-docs#14885

[nnja]

Hey, @cephalin This PR has been open for a few months now. Would you mind taking a look, or pointing me to the right person to review? Thank you.

[cephalin]

Hi Nina, since we chatted at that time, we've actually changed the Python tutorial to use Django instead. It's not even using this repo anymore. If you want me to merge it I still can.

[nnja]

@cephalin If this example isn't being actively used in the docs, what do you think about just removing it all together?