Travis: print acceptance tests logs in case of job failure

Because Travis doesn't allow us to keep files produced during tests
(such as log files), let's print the complete job log to the "console"
in case of job failures.

This is a debugging aid, and given that there's been some timeouts
happening on some tests, we absolutely needs the logs to have a proper
action.
Signed-off-by: NCleber Rosa <crosa@redhat.com>
Message-Id: <20190607152223.9467-2-crosa@redhat.com>
Reviewed-by: NWainer dos Santos Moschetta <wainersm@redhat.com>
Acked-by: NAlex Bennée <alex.bennee@linaro.org>
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>

.travis.yml

@@ -233,6 +233,8 @@ matrix:
     - env:
         - CONFIG="--python=/usr/bin/python3 --target-list=x86_64-softmmu,mips-softmmu,mips64el-softmmu,aarch64-softmmu,arm-softmmu,s390x-softmmu,alpha-softmmu"
         - TEST_CMD="make check-acceptance"
+      after_failure:
+        - cat tests/results/latest/job.log
       addons:
         apt:
           packages: