Executes all linters via pre-commit, which is much faster, guarantees
their version locking and allows upgrading them with a single command.
Before this change the only linter running via pre-commit was
ansible-lint.
Now we also run bashate, flake8 and yamllint via pre-commit.
For developer convenience we still keep the old tox environments
which allow running a single linter.
Change-Id: Ia0737c50de0f01de8576089d72de8940c16e9e0e
f0b251d924