Makes tests much more quietly, as opposed to the enormous amount of
logging that appears right now. This setting is used in AJ, as well as
other frameworks.
Output from test run:
```
.........................................................
Finished in 3.003355s, 18.9788 runs/s, 45.2827 assertions/s.
57 runs, 136 assertions, 0 failures, 0 errors, 0 skips
```
If you have a "service/configurations.yml" file, but every single line is
commented out, then an error occurs when running tests:
```
git:active-storage-import~/code/rails/activestorage$ rake
~/code/rails/activestorage/test/test_helper.rb:17:in `<top (required)>': undefined method `deep_symbolize_keys' for false:FalseClass (NoMethodError)
from ~/code/rails/activestorage/test/controllers/direct_uploads_controller_test.rb:1:in `require'
```
The reason is that `YAML.load(..an empty file content..)` simply returns `false`, and not `{}`.
This PR fixes this behavior so tests can also run when no remote service
is available.
