dockertest.subtest: Resolve minor fixme

* Sometimes warnings aren't logged, make sure this
  one gets noticed.

Signed-off-by: Chris Evich <cevich@redhat.com>
dockertest.subtest: Allow subtest imports

Both Subtests and sub-subtests are treated more like
plugins than actual python modules.  However this
introduces the problem that they cannot import modules
from their own directory w/o outside help/hacks.

This change modifies the default/example control file
to inject the subtest's full path at the beginning of
the module search path.  Success or failure it also
takes care of removing this modification and alterting
checking if the subtest left any further modifications.

Signed-off-by: Chris Evich <cevich@redhat.com>
dockertest.output: Remove disused variable

Signed-off-by: Chris Evich <cevich@redhat.com>
Docker: Pylint cleanup: unused imports

*  Disabled a few messages that can safely be ignored

Signed-off-by: Chris Evich <cevich@redhat.com>