Swap precedence ordering of user kitchen data over provided data.
Make Busser inherit test_base_path from Kitchen::Config.

This will allow for altering the test_base_path default of
"test/integration".
Expand all Chef-related local paths in Provisioner::ChefBase.

This should help to make all relative paths absolute, relative to
kitchen_root directory.

Debugging output should be clearer and less ambiguous:

    kitchen list --debug