fix: agent config not picked up from parameters

[lenkan]

When agent URLs where only provided through parameters (from env variables), the "dt" field was not set, which caused keripy to ignore the configuration. This PR ensure that "dt" field is set.

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 86.63%. Comparing base (1f22907) to head (e656d30). :warning: Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #397      +/-   ##
==========================================
+ Coverage   86.60%   86.63%   +0.03%     
==========================================
  Files          25       25              
  Lines        5286     5299      +13     
==========================================
+ Hits         4578     4591      +13     
  Misses        708      708              

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