Jenkinsfile hack for auto-cancellation.
Jenkinsfile hack for auto-cancellation.

This change will cause Jenkins to only build the
latest HEAD of a PR branch, cancelling any
previous builds that may already be in progress.
This will decrease feedback time and help mitigate
resource contention.

Signed-off-by: Peter Salvatore <4b8373d016f277527198385ba72fda0feb5da015@psftw.com>

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