Fix a prefix of it is already part of a volume on GlusterFS

If you have removed a GlusterFS brick and want to reuse it, you may encounter this error:

/path/app or a prefix of it is already part of a volume

Example GlusterFS add-brick command and error:

# gluster volume add-brick vol1 gluster-server1:/path/app
/path/app or a prefix of it is already part of a volume

# gluster volume create foo gluster-server1:/data gluster-server2:/data
/data or a prefix of it is already part of a volume

To resolve the problem: Run:

# setfattr -x trusted.glusterfs.volume-id /PATH
# setfattr -x trusted.gfid /PATH

Here, /PATH is the path of the brick to add or use when creating a volume.