chore(typing): clean up some of the workrounds from the initial PR

[ThosRTanner]

Why is this needed?

This addresses some of the issues spotted when adding type checking but left until later due to the extent of the initial pull request.

Proposed Changes

• Clean up the kazoo client init method to setup up the retry handlers and hosts lists more cleanly
• Some tests removed in because what was being tested would not have passed mypy were it not for the way self.assertRaises handles the parameter list.
• ...

Does this PR introduce any breaking change?

If anyone directly calls kazoo.hosts.collect_hosts it will no longer return None for the chroot. It will return "" in that situation. But that isn't part of the published API.

[codecov]

Codecov Report

❌ Patch coverage is 97.87234% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 95.45%. Comparing base (e894342) to head (d4b8623).
⚠️ Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
kazoo/client.py	97.14%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #801      +/-   ##
==========================================
- Coverage   96.65%   95.45%   -1.20%     
==========================================
  Files          27       27              
  Lines        3554     3832     +278     
==========================================
+ Hits         3435     3658     +223     
- Misses        119      174      +55     

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