subtests...cp: Convert to use sub-subtests

*  Added comment
*  Removed extended default timeout
*  Fixed string concatenation style
*  Use API method for container name generation

Signed-off-by: Chris Evich <cevich@redhat.com>
subtests...cp: Add every_last sub-subtest

* Feed container some python to walk it's entire filesystem
  except certain directories and symlinks as configured.
  Pickle results back to sub-subtest via stdout.
* Use the docker cp command on every file from unpickled
  list, verify it was copied to the host.

Signed-off-by: Chris Evich <cevich@redhat.com>
dockertest.dockercmd: More exception detail

Both NoFail and MustFail sub-classes provided very little
info. from exception in execute().  Added some overridable
static values with some simple default values.

Signed-off-by: Chris Evich <cevich@redhat.com>
subtests...cp: Fix style/comments.

Instead of naked try...except, rely on NoFailDockerCmd to
provide any debugging details.  Clarify comment regarding
command-line fed code-generation via inspect module.

Signed-off-by: Chris Evich <cevich@redhat.com>
subtests...cp: Limit max files to be copied

Signed-off-by: Chris Evich <cevich@redhat.com>
Merge pull request #281 from cevich/cp_anywhere

Add Docker cp anywhere