Refactor: CTS: Apply pylint and pyflake fixes to pacemaker-cts-dummyd.

• Get rid of the use of a global variable by returning the value from parse_args and passing it to every function that needs it.

• Disable the module name warning.

• Fix up docstrings.

• Add pacemaker-cts-dummyd to the list of files that can be checked in the Makefile.