info: add warnings about missing blkio cgroup support
info: add warnings about missing blkio cgroup support

These warnings were only logged, and could therefore be overlooked
by users. This patch makes these more visible by returning them as
warnings in the API response.

We should probably consider adding "boolean" (?) fields for these
as well, so that they can be consumed in other ways. In addition,
some of these warnings could potentially be grouped to reduce the
number of warnings that are printed.

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

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