avocado.plugins.vm: Add missing param for compatibility

We missed that on the whiteboard work.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
avocado.core.output: Add missing attribute for OutputManager

So the vm plugin can correctly determine the logs dir.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
.travis.yml: Add apt-get update

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
Merge pull request #126 from lmr/fix-vm-plugin

Fix vm plugin