avocado.job: Fix return code of stand alone tests

When running stand alone tests, ie, tests without
the avocado runner, I surely do expect they return
exit codes according to wether it passed or failed.

This patch fixed that by making the TestModuleRunner
class to return appropriate return codes from the
Job.run() function.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
.travis.yml: Run stand alone tests

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
Merge pull request #57 from avocado-framework/fix-stand-alone-tests-rc

Fix stand alone tests rc