Adds check if default ip address is correct format.

It avoids hidden error when ports are redirected from
container to host using -p host_port:guest_port.

Docker-DCO-1.1-Signed-off-by: Jiří Župka <jzupka@redhat.com> (github: jzupka)
Merge pull request #6234 from jzupka/fix_check_default_ip

Adds check if default ip address is correct format.