distribution/xfer: use "main" instead of "master" for progress channel
distribution/xfer: use "main" instead of "master" for progress channel

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

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