Changed refreshing federated token logic

[mariuszluciow]

Closes #796

Description of changes:

Changed logic of refresh to stop removing valid user if a refreshHandler is not configured for the provider.
Added a test.

Any suggestions are welcome.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-io]

Codecov Report

Merging #797 into master will decrease coverage by 0.02%.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##           master     #797      +/-   ##
==========================================
- Coverage   87.48%   87.46%   -0.03%     
==========================================
  Files          74       74              
  Lines        3557     3558       +1     
  Branches      679      680       +1     
==========================================
  Hits         3112     3112              
- Misses        423      424       +1     
  Partials       22       22

Impacted Files	Coverage Δ
packages/aws-amplify/src/Auth/Auth.ts	88.3% <77.77%> (-0.15%)	⬇️

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[powerful23]

👍 Thanks for fixing that!

[github-actions]

This pull request has been automatically locked since there hasn't been any recent activity after it was closed. Please open a new issue for related bugs.

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