fuel, armband: Add post mortem log collection

fuel, armband: Add post mortem log collection

Debugging test suite failures is often hard without physical access
to the POD, and even then the environment might be automatically
redeployed before successfully debugging the problem.

So, collect all contents of </var/log> from all cluster nodes
(including the Salt Master node) after all test suites have been
executed as part of the CI job.

Change-Id: Ie5e2526c74f4ed21be9c76c6f6101eb3f434be36
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>