Fix optimization bug add coverage plus

Fix optimization bug add coverage plus

Fix a NPE bug and add more code coverage.

Also is missing returning of context details for subscriber policies.

This code is a bit ad-hoc and there is a separate JIRA POLICY-2147 to
support re-factoring this codebase.

Added scanning for advice to be returned. For optimization, because of
the need for some changes in XACML github dependency, we are stuck with
a little narly code to get it to fully work. POLICY-2417 is created to
address this in Guilen.

Upgraded to released XACML artifact - this has been tested locally for
a few weeks with naming, guard and this optimzation code. It removed
Jackson in lieu of Json, cleaned up some security fixes, upgraded
dependencies, and added more code coverage.

Issue-ID: POLICY-2066
Change-Id: I3cae99de265c815200ec2ce71e471338772bdb5b
Signed-off-by: Pamela Dragosh <pdragosh@research.att.com>