opts: code clean up

opts/hostcfg.go

opts/hostcfg_test.go

opts/integration_test.go

opts/json.go

opts/json_test.go

opts/opts.go

opts/opts_test.go

opts/security.go

opts/security_test.go

opts/testdata/unmarshal/bad_json.json

opts/testdata/unmarshal/host_auth_bad_type.json

opts/testdata/unmarshal/host_auth_good.json

opts/testdata/unmarshal/host_dns_bad_type.json

opts/testdata/unmarshal/host_dns_bad_value.json

opts/testdata/unmarshal/host_dns_good.json

opts/testdata/unmarshal/host_gateway_bad_type.json

opts/testdata/unmarshal/host_gateway_bad_value.json

opts/testdata/unmarshal/host_gateway_good.json

opts/testdata/unmarshal/host_good_additional_key.json

opts/testdata/unmarshal/host_good_empty.json