Fix outdated comment in rootwrap filter
GlusterFS volume driver has been removed[1], and chgrp is now used
in NFS backup driver and GlusterFS backup driver.
[1]
@@ -95,7 +95,8 @@ rm: CommandFilter, rm, root
# cinder/volume/drivers/netapp/dataontap/nfs_base.py:
netapp_nfs_find: RegExpFilter, find, root, find, ^[/]*([^/\0]+(/+)?)*$, -maxdepth, \d+, -name, img-cache.*, -amin, \+\d+
-# cinder/volume/drivers/glusterfs.py
+# cinder/backup/drivers/nfs.py
+# cinder/backup/drivers/glusterfs.py
chgrp: CommandFilter, chgrp, root
# cinder/brick/initiator/connector.py:
