Add a fallback URL for NeuroMorpho API health check

[IgorTatarnikov]

Currently, http://cng.gmu.edu:8080/api/health returns a 503 when queried. Interestingly, if you query the API regardless it returns valid output e.g. http://cng.gmu.edu:8080/api/neuron/id/1.

This PR adds a fallback URL for querying API health if http://cng.gmu.edu:8080/api/health doesn't return 200. In this case self._base_url is swapped for http://neuromorpho.org/api/neuron instead of http://cng.gmu.edu:8080/api/neuron.

[codecov]

Codecov Report

Attention: Patch coverage is 77.77778% with 2 lines in your changes missing coverage. Please review.

Project coverage is 72.37%. Comparing base (bb21a0c) to head (f26038f).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
morphapi/api/neuromorphorg.py	77.77%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #96      +/-   ##
==========================================
+ Coverage   72.14%   72.37%   +0.23%     
==========================================
  Files          10       10              
  Lines         718      724       +6     
==========================================
+ Hits          518      524       +6     
  Misses        200      200              

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