multiple jenkins webhooks cause duplicate status in gitlab

## Issue
multiple jenkins webhooks cause duplicate status in gitlab

### Context
- **Gitlab plugin version**: 1.6
- **Gitlab version**: 13.8.0-ee
- **Jenkins version**: 2.235.5
- **Job type**: Freestyle

### Logs & Traces

We haven't found anything significant in either jenkins or gitlab logs.

### Problem description

- set up 2 web hooks in a single gitlab repo to jenkins
- set up both jenkins jobs to publish status back to the same gitlab repo (NB: that this issue doesn't occur if either job does NOT have the publish option enabled)
- each commit to an MR will trigger the 2 jobs, but the pipelines that come back will have a duplicate.
- See screenshots below (there is a bundled ops-jenkins central-... and a separate ops-jenkins central..)
- The separate one never completes (presumably because the duplicate bundled one already got the notification that the job ended so the solo one will never get a notification)
- It's not the same job that's duplicated each time... it flips back and forth.

First status hover screenshot:
Second status hover screenshot: