Improve ONAP-PDP-REST JUnit test case independency

Handle cleanup of changed system properties and other test-related
static parameters to prevent unexpected behaviour of other test cases
that are dependent of the same properties and parameters when order
of the execution changes

Add Samsung modification copyrights for changed files

Fix some loggings and a minor typo in documentation

Change-Id: Ib6920d6300da79bfc426e4f348b503e3fd6a31ee
Issue-ID: POLICY-1501
Signed-off-by: kaihlavi <l.kaihlavirt@partner.samsung.com>