Xapp-frame, v0.8.1 Rest Subscription Creation /Query /Deletion

Xapp-frame, v0.8.1 Rest Subscription Creation /Query /Deletion

Convert RMR unittest cases to REST API based
* Fixed REST endpoint construction functionality to include correct port numbers in endpoint string
* Added a REST version of a testcase TestSubReqAndRouteUpdateNok
* Refactored ut_stub REST endpoint setting API and restored original port numbers.

Xapp-frame, v0.8.1 integration:
  * Added REST API based unit test cases

Change-Id: I0989939f4210692493de549380faa1f111d71435
Signed-off-by: Konstantinos Archangelof <konstantinos.archangelof@nokia.com>