libcontainerd/supervisor: store location of config-file
libcontainerd/supervisor: store location of config-file

Adding a remote.configFile to store the location instead of re-constructing its
location each time. Also fixing a minor inconsistency in the error formats.

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

trebonian/docker,mahak/docker,jimjag/docker,thaJeztah/docker,Mokolea/docker,konstruktoid/docker-upstream,trebonian/docker,jimjag/docker,konstruktoid/docker-upstream,moby/moby,moby/moby,Ramzec/docker,Mokolea/docker,cpuguy83/docker,moul/docker,thaJeztah/docker,mahak/docker,mahak/docker,konstruktoid/docker-upstream,moul/docker,Mokolea/docker,thaJeztah/docker,jimjag/docker,Ramzec/docker,moul/docker,moby/moby,cpuguy83/docker,Mokolea/docker,cpuguy83/docker,Ramzec/docker,mahak/docker,moul/docker,moby/moby,jimjag/docker,Ramzec/docker,cpuguy83/docker,thaJeztah/docker,trebonian/docker,trebonian/docker,konstruktoid/docker-upstream