IANA allocated Docker port: 2375

2375/2376 are assigned:
http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=docker

For #1440

Docker-DCO-1.1-Signed-off-by: SvenDowideit <SvenDowideit@home.org.au> (github: SvenDowideit)