Run HAProxy in a chroot jail

It's impossible to drop root for the HAProxy container.
But HAProxy provides a possibility to use a chroot jail.

When attaching to the HAProxy container, we see that
the root directory is changed:

    $ sudo docker exec -ti haproxy bash
    (haproxy)[root@operator /]# ls -di /
    259 /

Co-Authored-By: Vikram Hosakote <vhosakot@cisco.com>

Closes-Bug: #1552289

Change-Id: I9d55e9b741b8560cac53dc8b837a24a3029a4dc0