Add CurrentContainerID into Docker struct

[baptistedonaux]

Add CurrentContainerID into Docker struct. This improvement allow the possibility to compare current container networks and others containers networks.

@md5 I watched your comments and I edited my code to propose a best version.

Linked with nginx-proxy/nginx-proxy#337

[baptistedonaux]

Success Travis !

[md5]

This is looking pretty good. I'm curious about baptistedonaux@b3b09d7 though. If different Docker versions have a different name for the cgroups, it might be good to support both formats. I've only seen the slash version looking at Docker 1.9 and 1.10.

I still think this code needs to have a test or two.

Also, I'd recommend initializing the regex as a const instead of compiling it each time the function runs.

[baptistedonaux]

About baptistedonaux@b3b09d7 I had Docker 1.9.1 and works on Debian Jessie. Unfortunately I can't reproduce.

I will change my code with your comments. For the test, it's tests in code or unit test ?

[baptistedonaux]

Travis success. Ready to be merged ! @jwilder @md5

[md5]

This log line is going to make docker-gen noisy when it runs outside a container. I don't think it's necessary.

[baptistedonaux]

Edited !

[jwilder]

Thanks @baptistedonaux @md5!