enable canary for EI supported regions

[ChoiByungWook]

Description of changes:
Enabling the tests specified here as canaries: #527

The regions were determined based on: https://aws.amazon.com/machine-learning/elastic-inference/pricing/

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[codecov-io]

Codecov Report

Merging #584 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #584   +/-   ##
=======================================
  Coverage   92.78%   92.78%           
=======================================
  Files          71       71           
  Lines        5366     5366           
=======================================
  Hits         4979     4979           
  Misses        387      387

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