Use the session profile to write when running aws configure

[joguSD]

Previously the command aws configure would only use the profile present in the parsed globals to pass to the ConfigFileWriter, but sourced the profile from the session everywhere else. This would cause issues when the profile is set via an environment variable as the updated values would be written to the wrong section. This updates the configure command to consistently use the profile on the session and updates the unit test to rely on the session rather than the parsed globals.

Fixes #2970

[jamesls]

Changelog entry please.

[codecov-io]

Codecov Report

Merging #2972 into develop will decrease coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop    #2972      +/-   ##
===========================================
- Coverage    95.69%   95.69%   -0.01%     
===========================================
  Files          159      159              
  Lines        12036    12030       -6     
===========================================
- Hits         11518    11512       -6     
  Misses         518      518

Impacted Files	Coverage Δ
awscli/customizations/configure/configure.py	100% <100%> (ø)	⬆️
awscli/clidriver.py	96.6% <0%> (-0.04%)	⬇️
awscli/customizations/emr/createcluster.py	98.23% <0%> (-0.02%)	⬇️
awscli/customizations/emr/helptext.py	100% <0%> (ø)	⬆️
awscli/customizations/emr/argumentschema.py	100% <0%> (ø)	⬆️

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