Capture flex plugin logs

[JohnStrunk]

The flex DS should have a sidecar(s) that:

• provides the flex logfile to stdout
• provides the fuse log to stdout
• properly rotates the log files to prevent space exhaustion

[JohnStrunk]

Looks like glusterfs needs to be HUP-ed after rotation: https://github.com/gluster/glusterfs/blob/master/extras/glusterfs-logrotate We need to figure out how to do that from the container, given that glusterfs fuse process is running on the host.