Docker flow improvements #1114

[seth2810]

1. Using a lighter ansible image in docker and cleanup after done
2. Using a lighter postgres image in docker

relates to #1114

[codecov-commenter]

Codecov Report

Merging #1115 (2b74892) into master (2e4cb0d) will not change coverage.
The diff coverage is n/a.

❗ Current head 2b74892 differs from pull request most recent head b4af782. Consider uploading reports for the commit b4af782 to get more accurate results

@@           Coverage Diff           @@
##           master    #1115   +/-   ##
=======================================
  Coverage   70.01%   70.01%           
=======================================
  Files         125      125           
  Lines        2608     2608           
=======================================
  Hits         1826     1826           
  Misses        782      782           

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