containerd.installer: refactor
containerd.installer: refactor

- add `set -e` to prevent linting warnings
- use `install` instead of `cp`
- use a subshell for the whole function, instead of starting one
  inside it.

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

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