Fix: Avoid https_client_test_net Hang If No Network

[dgreatwood]

We avoid the test hangs seen previously by catching the exception that Pistache generates if there is no network connected.

Also - Added a test to check that the exception is correctly generated if the client tries to connect to a non-existent URI.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.33%. Comparing base (94be9f0) to head (a0301c5).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1301      +/-   ##
==========================================
+ Coverage   75.97%   76.33%   +0.35%     
==========================================
  Files          63       64       +1     
  Lines        9851    10972    +1121     
==========================================
+ Hits         7484     8375     +891     
- Misses       2367     2597     +230     

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