Convert rspec-system tests to beaker-rspec.

This work migrates the existing tests to beaker-rspec.
Merge pull request #273 from apenney/add-beaker-tests

Convert rspec-system tests to beaker-rspec.
Merge pull request #270 from phemmer/nat_input

allow input chain in nat table
Merge pull request #271 from phemmer/fix_builtin_chains

fix handling of builtin chains
Merge pull request #268 from phemmer/ipsec_support

add ipsec policy matching
Merge pull request #267 from phemmer/negation_support

Negation support
add support for removing unmanaged firewall rules
add specs for chain purge