Move integration xtesting Dockerfile to ONAP

Move integration xtesting Dockerfile to ONAP

All the Dockerfiles and xtesting configurations were hosted in gitlab.com [1]
The goal of this patch is to host these assets in ONAP
A jenkins jjb shall be created to generated the docker and push them on the nexus
(today the built-in registry of ONAP was used)

These xtesting dockers are referencing integration categories [2] and integration
use cases [3]
These xtesting dockers shall also simplify the way to integrate new use cases in any
CI chain (jenkins or gitlab-ci based)

[1]: https://gitlab.com/Orange-OpenSource/lfn/onap/integration/xtesting
[2]: https://wiki.onap.org/pages/viewpage.action?pageId=71835330
[3]: http://testresults.opnfv.org/onap/api/v1/projects/integration/cases

Issue-ID: INT-1366

Signed-off-by: mrichomme <morgan.richomme@orange.com>
Change-Id: Iba0fc0b0415731a7a81ba0225a70ae16391dd129
Signed-off-by: mrichomme <morgan.richomme@orange.com>