Set container MAC with run parameter and show link-local IPv6 at inspect

This Pull Request depends on https://github.com/docker/libcontainer/pull/208
Related Issues: https://github.com/docker/docker/issues/4918, https://github.com/docker/docker/issues/4033

I have implemented a functionality to set the container's mac address explicitly.
Further docker inspect will display the MAC address as well as the container's link-local IPv6 address.

    # host$ docker run -i -t --mac-address=26:99:7c:50:d8:20 --name=my-container ubuntu bash

    # my-container$ ifconfig eth0
    eth0      Link encap:Ethernet  HWaddr 26:99:7c:50:d8:20
              inet addr:172.17.0.4  Bcast:0.0.0.0  Mask:255.255.0.0
              inet6 addr: fe80::2499:7cff:fe50:d820/64 Scope:Link
              UP BROADCAST  MTU:1500  Metric:1
              RX packets:1 errors:0 dropped:0 overruns:0 frame:0
              TX packets:1 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:1000
              RX bytes:90 (90.0 B)  TX bytes:90 (90.0 B)

    # host$ docker inspect my-container
    ...
    "NetworkSettings": {
        "Bridge": "docker0",
        "Gateway": "172.17.42.1",
        "IPAddress": "172.17.0.2",
        "IPPrefixLen": 16,
        "LinkLocalIPv6Address": "fe80::2499:7cff:fe50:d820",
        "LinkLocalIPv6PrefixLen": 64,
        "MacAddress": "26:99:7c:50:d8:20",
        "PortMapping": null,
        "Ports": {}
    },
    ...

I am not sure what is the problem with Travis. It says `mkdir: cannot create directory '/precompiled': Permission denied`. On my machine `make test-unit` and `make test-integration` work fine. I would appreciate your help.

This is one of the first steps of full IPv6 integration in docker.
Currently I have a running IPv6 implementation that I am breaking down into multiple Pull-Requests to simplify review and merging.

I would like to get some feedback.