subtests.docker_cli: Add ps_size test

This test executes couple of containers, creates file in each of them
and compares the size of the container with the size of the created file.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
dockertest: Mask unittest magic found by new pylint

Latest pylint run by Travis complains about
  Bad first argument 'FakeSubtestException' given to super()
As this is intended in unittest I masked it localy...

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
Merge branch 'ps_size' of https://github.com/ldoktor/autotest-docker
subtests.docker_cli: Update ps_size docs

Signed-off-by: Chris Evich <cevich@redhat.com>
Merge pull request #289 from cevich/master

Small doc. fixup for #286