Adding retries option to override default value 3 of urllib3

[chowmean]

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh, ./bin/openapi3/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\.
• Filed the PR against the correct branch: master, 3.4.x, 4.0.x. Default: master.
• Copied the technical committee to review the pull request if your PR is targeting a particular programming language.

Description of the PR

Adding retries option to override the default value of urllib which is 3. This will give option to control number of retries for any request.

[wing328]

@chowmean thanks for the PR. Can you please also update the Python Petstore samples by running the shell scripts (./bin/python*) or batch files under (bin\windows\python*) ?

[wing328]

cc @taxpon (2017/07) @frol (2017/07) @mbohlool (2017/07) @cbornet (2017/09) @kenjones-cisco (2017/11) @tomplus (2018/10) @Jyhess (2019/01)

[chowmean]

@chowmean thanks for the PR. Can you please also update the Python Petstore samples by running the shell scripts (./bin/python*) or batch files under (bin\windows\python*) ?

Ran the ensure_upto_date which runs all the scripts. I guess that is fine? @wing328

[wing328]

Yup, and all tests passed 👍

[wing328]

LGTM