Snap promotion fix

Changes snapcraft to run directly on host instead of in docker
continer.  This adds the requirement to have snapcraft installed
in the Jenkins agent, but is more reliable as the snapcraft docker
image is not the best practice anymore for building snaps.

Back ported new license scan.

Change-Id: I21da8a2d38671fc7b253cb6e19a8afb1f1e6acb6
Signed-off-by: beierlm <mark.beierl@canonical.com>