Fluentd: extract parsing config, and validate early
Fluentd: extract parsing config, and validate early

This extracts parsing the driver's configuration to a
function, and uses the same function both when initializing
the driver, and when validating logging options.

Doing so allows validating if the provided options are in
the correct format when calling `ValidateOpts`, instead
of resulting in an error when initializing the logging driver.

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

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