avocado.test: Correctly set self.tag when auto tagging

The auto tag feature was leaving self.tag unset, which
is not the behavior we want. Fix it.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
unittests/avocado: Add test_unittest.py

Simple unittest for the Test and Dropin class implementations.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
Merge pull request #33 from avocado-framework/test-unittest

Test unittest