Fix fetch action plugin to not fail if file is missing and fail_if_missing=False (the default).  Add tests to test_fetch role to verify it works as expected.

Remove the legacy templating code, which was guarded by deprecation warnings in the previous two releases, and undocumented for a long time.  use {{ foo }} to access variables instead of ${foo} or $foo.

Some systems that we are testing on may not have /etc/motd. So we need to create a file that we can control and use that for the further tests.