Add test for #8307.

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
iptables cleanup success on daemon restart for closing 8307

Signed-off-by: Jessica Frazelle <jess@docker.com>

Docker-DCO-1.1-Signed-off-by: cc272309126 <cc272309126> (github: jfrazelle)