[TASK] Provide behat context traits for isolated security testing (Revision 4)

Security features mostly have to be tested in a subprocess, as
we have to recreate proxies for the specified testing policy.

This change provides a trait, to run behat steps in an isolated process,
as well as a trait to test security features.

Change-Id: I7ba61a8e49d108b685394a70be8657550c4033aa
Releases: master
Revision-Id: 6e5791ce0897c9d47f9c6485e8ab23d69998c003