Docker on CentOS 7, gelf log-driver doesn't exist

Docker Engine General
1

On CentOS 7, when I try to use the gelf log-driver like so:

docker run -d --name turd  --log-driver=gelf --log-opt gelf-address=udp://foo.example.com:12201 --log-opt tag="test" alpine /bin/sh -c "while true; do echo My Message \$RANDOM; sleep 5; done;"

this is written to docker logs:

"logs" command is supported only for "json-file" and "journald" logging drivers (got: gelf)

docker inspect turd returns:

        "HostConfig": {
            "Binds": null,
            "ContainerIDFile": "",
            "LogConfig": {
                "Type": "gelf",
                "Config": {
                    "gelf-address": "udp://foo.example.com:12201",
                    "tag": "test"
                }
            },
```

I have logstash configured to listen:

```
input {
    tcp {
        port => 10500
    }
    gelf {
    }
}

output {
    elasticsearch {
        hosts => ["foo.example.com:9200"]
        user  => 'elastic'
        password => 'changeme'
    }
}
```

`docker info` returns:

```
[root]# docker info
Containers: 12
 Running: 12
 Paused: 0
 Stopped: 0
Images: 34
Server Version: 1.13.0
Storage Driver: overlay
 Backing Filesystem: xfs
 Supports d_type: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
 Volume: local
 Network: bridge host macvlan null overlay
Swarm: active
 NodeID: 8ld3vo1wypixghhzxx7x53fd2
 Is Manager: true
 ClusterID: c74e0jm5efzrpt45tagk9bjmz
 Managers: 1
 Nodes: 4
 Orchestration:
  Task History Retention Limit: 5
 Raft:
  Snapshot Interval: 10000
  Number of Old Snapshots to Retain: 0
  Heartbeat Tick: 1
  Election Tick: 3
 Dispatcher:
  Heartbeat Period: 5 seconds
 CA Configuration:
  Expiry Duration: 3 months
 Node Address: 10.205.45.208
 Manager Addresses:
  10.205.45.208:2377
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 03e5862ec0d8d3b3f750e19fca3ee367e13c090e
runc version: 2f7393a47307a16f8cee44a37b262e8b81021e3e
init version: 949e6fa
Security Options:
 seccomp
  Profile: default
Kernel Version: 3.10.0-514.2.2.el7.x86_64
Operating System: CentOS Linux 7 (Core)
OSType: linux
Architecture: x86_64
CPUs: 4
Total Memory: 7.64 GiB
Name: cocreate-centos7
ID: KJVX:RIKV:EDJY:PGKQ:I7BR:GYF3:HQCD:X6DF:ULIL:IOJK:XPNL:LD24
Docker Root Dir: /docker/var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
Experimental: false
Insecure Registries:
 127.0.0.0/8
Live Restore Enabled: false
```

I'm stuck.  Is this a configuration issue or a CentOS/Docker issue?