Add the memory swappiness tuning option to docker.

Memory swappiness option takes 0-100, and helps to tune swappiness
behavior per container.
For example, When a lower value of swappiness is chosen
the container will see minimum major faults. When no value is
specified for memory-swappiness in docker UI, it is inherited from
parent cgroup. (generally 60 unless it is changed).

Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>