config: use the right API to access template access
Preventing direct access to the underlying dict will help a coming refactoring
of `config`.
Differential Revision: https://phab.mercurial-scm.org/D9922
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.