daemon/config: fix TestReloadDefaultConfigNotExist if file exists
daemon/config: fix TestReloadDefaultConfigNotExist if file exists

The TestReloadDefaultConfigNotExist() test assumed it was running in a clean
environment, in which the `/etc/docker/daemon.json` file doesn't exist, and
would fail if that was not the case.

This patch updates the test to override the default location to a a non-existing
path, to allow running the test in an environment where `/etc/docker/daemon.json`
is present.

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

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