This fixes a bunch of minor pylint warnings:
* Drop unused imports.
* Fix "inline-JSON" formatting.
* Fix space before/after brackets.
* Use `_` for unused variables.
* Break overlong lines.
* Mark unittest as `no-self-use` if applicable.
* Drop spurious newline at end of file.
Add a helper, `parse_config`, to parse a selinux configuration file,
see selinux(8), and return a dictionary containing the configuration
data in key, value pairs. This, in turn, can be fed into the other
helper method, `config_get_policy`, to get the effective policy or
`None` if SELinux is disabled or the policy type is not configured.
Add a new test suite that checks the basic functionality of the
helpers above.
