Jenkinsfile: set repo and branch, to assist validate_diff()
Jenkinsfile: set repo and branch, to assist validate_diff()

This is a continuation of 2a08f33166247da9d4c09d4c6c72cbb8119bf8df;

When running CI in other repositories (e.g. Docker's downstream
docker/engine repository), or other branches, the validation
scripts were calculating the list of changes based on the wrong
information.

This lead to weird failures in CI in a branch where these values
were not updated ':-) (CI on a pull request failed because it detected
that new tests were added to the deprecated `integration-cli` test-suite,
but the pull request did not actually make changes in that area).

This patch uses environment variables set by Jenkins to sets the
correct target repository (and branch) to compare to.

Signed-off-by: Sebastiaan van Stijn <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@gone.nl>

paralin/docker,djs55/docker,vdemeester/docker,konstruktoid/docker-upstream,ibuildthecloud/docker,trebonian/docker,konstruktoid/docker-upstream,AkihiroSuda/docker,Mokolea/docker,flavio/docker,jvanz/docker,cpuguy83/docker,konstruktoid/docker-1,moby/moby,yongtang/docker,ibuildthecloud/docker,nalind/docker,djs55/docker,moul/docker,kojiromike/docker,jameszhan/docker,yosifkit/docker,cpuguy83/docker,mahak/docker,docker/docker,gnailuy/docker,justincormack/docker,Ramzec/docker,estesp/docker,pradipd/moby,flavio/docker,nawawi/docker,justincormack/docker,jthelin/docker,bearstech/moby,paralin/docker,cpuguy83/docker,gnailuy/docker,jvanz/docker,jimjag/docker,yosifkit/docker,cpuguy83/docker,pradipd/moby,docker/docker,paralin/docker,yongtang/docker,yosifkit/docker,thaJeztah/docker,konstruktoid/docker-upstream,ibuildthecloud/docker,yosifkit/docker,SvenDowideit/docker,pradipd/moby,konstruktoid/docker-upstream,ibuildthecloud/docker,Mokolea/docker,jameszhan/docker,Ramzec/docker,moul/docker,flavio/docker,ibuildthecloud/docker,nawawi/docker,bearstech/moby,Mokolea/docker,flavio/docker,mahak/docker,paralin/docker,gnailuy/docker,trebonian/docker,nawawi/docker,estesp/docker,jimjag/docker,jvanz/docker,SvenDowideit/docker,kojiromike/docker,AkihiroSuda/docker,yongtang/docker,Ramzec/docker,mahak/docker,nalind/docker,dims/docker,estesp/docker,SvenDowideit/docker,nawawi/docker,dims/docker,nalind/docker,kojiromike/docker,jimjag/docker,moby/moby,docker/docker,thaJeztah/docker,bearstech/moby,konstruktoid/docker-1,gnailuy/docker,moby/moby,trebonian/docker,thaJeztah/docker,bearstech/moby,moby/moby,Mokolea/docker,justincormack/docker,jimjag/docker,vdemeester/docker,Ramzec/docker,mahak/docker,djs55/docker,jameszhan/docker,AkihiroSuda/docker,jthelin/docker,vdemeester/docker,nalind/docker,moul/docker,AkihiroSuda/docker,konstruktoid/docker-1,thaJeztah/docker,trebonian/docker,dims/docker,moul/docker