Copy module was walking over files in subdirectories repeatedly (a
directory tree a few levels deep could bring the time spent into the
tens of minutes)
This was traced to the fix for this bug report: https://github.com/ansible/ansible/issues/13013Fixed#13013 a different way and added an integration test to check for
regressions of #13013 as we optimize this code.
Fixes#21513
This change corrects problems reported by the `yamllint` linter.
Since key duplication problems were removed in 4d48711, this commit
mainly fixes trailing spaces and extra empty lines at beginning/end of
files.
