travis.yml: avocado: Print logs of non-pass tests only

travis.yml: avocado: Print logs of non-pass tests only

The acceptance tests build on Travis is configured to print
the entire Avocado's job log in case any test fail. Usually one is
interested on failed tests only though. So this change the Travis
configuration in order to show the log of tests which status is
different from 'PASS' and 'SKIP' only. Note that 'CANCEL'-ed tests
will have the log printed too because it can help to debug some
condition on CI environment which is not being fulfilled.

Signed-off-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20191230184327.2800-2-wainersm@redhat.com>