Fluentd collected metric should track either /var/log/pods or /var/log/containers

Node logs recently moved from being stored in /var/log/containers to /var/log/pods. Before this update, only the newer '/pods' directory was monitored, so there were no metrics on older openshift releases that use '/containers'. With this update, metrics will be collected from whichever directory is in use, so it works on old and new openshift releases. Also with this change, the "path" label is no longer set in the metrics. Changes in the way log files are named make it meaningless to use the "path" as a label. Instead use labels podname, containername etc. to identify log streams by containers.