Increase Max timeout for `get_ursulas`/`bucket_sampling`; fix faulty env variable usage

[derekpierre]

Type of PR:

• [x] Bugfix
• [ ] Feature
• [ ] Documentation
• [ ] Other

Required reviews:

• [ ] 1
• [x] 2
• [ ] 3

What this does:

• Increase max timeouts for now for /get_ursulas and /bucket_sampling - separate investigation can be done into efficiency improvements (#78)
• Separate default timeout from max timeout, especially now that the max timeout has been extended
• Fix bug where environment variables, when set, were incorrectly used as strings - cast values obtained from environment variables to integers.

Issues fixed/closed:

• Fixes #...

Why it's needed:

Explain how this PR fits in the greater context of the NuCypher Network. E.g., if this PR addresses a nucypher/productdev issue, let reviewers know!

Notes for reviewers:

What should reviewers focus on? Is there a particular commit/function/section of your PR that requires more attention from reviewers?

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 90.57%. Comparing base (d540b7c) to head (8224acc).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## development #77 +/- ## =============================================== + Coverage 90.55% 90.57% +0.02% =============================================== Files 18 18 Lines 900 902 +2 =============================================== + Hits 815 817 +2 Misses 85 85 ```

:umbrella: View full report in Codecov by Sentry.
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[theref]

separate investigation can be done into efficiency improvments

is there an issue for this?

[derekpierre]

separate investigation can be done into efficiency improvments

is there an issue for this?

There is one now - https://github.com/nucypher/nucypher-porter/issues/78 - 😆