registry/storage: ignore missing tag on delete
registry/storage: ignore missing tag on delete

Signed-off-by: Stephen J Day <63efd86fa22882ae89b6027b22a36e4db1f4214d@docker.com>

manoj535/distribution,thaJeztah/distribution,jwhonce/distribution,sadlil/distribution,konstruktoid/distribution,estesp/distribution,konstruktoid/distribution,jwhonce/distribution,manoj535/distribution,sadlil/distribution,docker/distribution,dmcgowan/distribution,vdemeester/distribution,duglin/distribution,miminar/distribution,duglin/distribution,yuwaMSFT2/distribution,estesp/distribution,sergeyfd/distribution,sergeyfd/distribution,yuwaMSFT2/distribution,mikebrow/distribution,miminar/distribution,mikebrow/distribution,docker/distribution,vdemeester/distribution,thaJeztah/distribution,dmcgowan/distribution