fix retire worker using tsa-team-authorized-keys only
fix retire worker using tsa-team-authorized-keys only

Fix issue : Not able to retire worker using tsa-team-authorized-keys only #3549

Before the patch :

```
root@01993a002c30:/src# concourse retire-worker --name $HOSTNAME
{"timestamp":"2019-05-28T12:02:56.757975470Z","level":"error","source":"retire-worker","message":"retire-worker.run.command-failed","data":{"command":"retire-worker","error":"Process exited with status 1","session":"2"}}
Process exited with status 1

{"timestamp":"2019-05-28T12:02:56.594409936Z","level":"debug","source":"atc","message":"atc.build-tracker.track.start","data":{"session":"16.27"}}
{"timestamp":"2019-05-28T12:02:56.597415009Z","level":"debug","source":"atc","message":"atc.build-tracker.track.done","data":{"session":"16.27"}}
{"timestamp":"2019-05-28T12:02:56.757792903Z","level":"error","source":"tsa","message":"tsa.connection.channel.exited-with-error","data":{"error":"key is authorized for team foo, but worker is global","remote":"172.18.0.4:60902","session":"27.1"}}
```

After the patch :

```
root@01993a002c30:/src# concourse retire-worker --name $HOSTNAME --team foo
{"timestamp":"2019-05-28T12:03:39.303142352Z","level":"debug","source":"retire-worker","message":"retire-worker.run.command-exited","data":{"command":"retire-worker","session":"2"}}

{"timestamp":"2019-05-28T12:05:01.499302164Z","level":"info","source":"tsa","message":"tsa.connection.channel.command.start","data":{"command":"retire-worker","remote":"172.18.0.4:32838","session":"46.1.1"}}
{"timestamp":"2019-05-28T12:05:01.516087207Z","level":"info","source":"tsa","message":"tsa.connection.channel.command.end","data":{"command":"retire-worker","remote":"172.18.0.4:32838","session":"46.1.1"}}
```

Signed-off-by: gaelL <1a73af9e7ae00182733b2292511b814be66f065f@gaell.info>

concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse