Refresh token should use the persistent session

[lmazuel]

No description provided.

[codecov-io]

Codecov Report

Merging #91 into master will increase coverage by 0.15%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master      #91      +/-   ##
==========================================
+ Coverage   28.94%   29.09%   +0.15%     
==========================================
  Files         380      380              
  Lines       16332    16176     -156     
==========================================
- Hits         4727     4707      -20     
+ Misses      11605    11469     -136

Impacted Files	Coverage Δ
msrest/service_client.py	81.69% <33.33%> (-1.41%)	⬇️
test/vanilla/AcceptanceTests/test_url.py	22.72% <0%> (+0.17%)	⬆️
...t/vanilla/AcceptanceTests/test_model_flattening.py	21.66% <0%> (+1.29%)	⬆️
test/vanilla/AcceptanceTests/test_dictionary.py	13.04% <0%> (+1.88%)	⬆️
.../vanilla/AcceptanceTests/test_required_optional.py	31.25% <0%> (+3.97%)	⬆️

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