Description of problem:
Default ACL cannot be removed.

Version-Release number of selected component (if applicable):
glusterfs 3.12.6-1.el7 from centos-gluster312 repository

How reproducible:
Always

Steps to Reproduce:

1. Create a new directory and set default ACL.

$ mkdir test
$ setfacl -m d:g::rwx test
$ getfacl test
# file: test
# owner: root
# group: root
user::rwx
group::r-x
other::r-x
default:user::rwx
default:group::rwx
default:other::r-x

2. Remove the default ACL. The command completes with no error, but default ACL is not removed.

$ setfacl -k test

Actual results:

$ getfacl test
# file: test
# owner: root
# group: root
user::rwx
group::r-x
other::r-x
default:user::rwx
default:group::rwx
default:other::r-x

Expected results:

$ getfacl test
# file: test
# owner: root
# group: root
user::rwx
group::r-x
other::r-x

Additional info:

I have a replicated volume with 2 nodes, and the operation was done from a fuse client.

Volume Name: www
Type: Replicate
Volume ID: 797ded04-3a3b-497a-a16b-15a75f7e1550
Status: Started
Snapshot Count: 0
Number of Bricks: 1 x 2 = 2
Transport-type: tcp
Bricks:
Brick1: fs21.localdomain:/glusterfs/www/brick1/brick
Brick2: fs22.localdomain:/glusterfs/www/brick1/brick
Options Reconfigured:
changelog.changelog: on
geo-replication.indexing: on
performance.client-io-threads: off
network.ping-timeout: 10
server.manage-gids: on
storage.build-pgfid: on
transport.address-family: inet
nfs.disable: on