syslog-address with tcp+tls protocol rejected by docker run

[jbergknoff]

I see the following behavior trying to use the new tcp+tls transport for the syslog log driver:

$ docker run --rm --log-driver=syslog --log-opt syslog-address=tcp+tls://logs.papertrailapp.com:1234 alpine:3.3 echo hello world
docker: Error response from daemon: syslog-address should be in form proto://address, got tcp+tls://logs.papertrailapp.com:1234.
$ docker -v
Docker version 1.10.0, build 590d5108

It looks like the relevant code is here: urlutil.

[thaJeztah]

This was added in #18998, looks indeed that tcp+tls was added there, but the validation was not updated.

ping @calavera