Made append_ip_rule() into a wrapper for add_ip_rule(), state tracking bug fixes

Made append_ip_rule() into a wrapper for add_ip_rule(), state tracking bug fixes

- Simplified append_ip_rule() to just be a wrapper around add_ip_rule(),
  which was updated to allow the value "-1" to be passed in as the rule
  insertion number in order to denote "append" (-A <chain>) mode.
- Added "mac_source" tests to t/basic_tests.pl.
- Bug fix to ensure that state tracking arguments are properly processed
  by add_ip_rule().