Some jobs won't run trigger if branch name is equal in two different repositories

## Issue
Jenkins job triggered but not run if branch name is equal in two or more different repositories

### Context
- **Gitlab plugin version**: 1.5.10
- **Gitlab version**: 11.8.0
- **Jenkins version**: 2.121.3
- **Job type**: Pipeline

### Logs & Traces

### Problem description
For the test case i used 3 GITLAB repositories:
1. bla-service
2. good-service
3. third-service
In each repo i have setup some branch

```
bla-service:aaa
good-service:bbb
third-service:ccc
```

They are all configured in gitlab to trigger the same Jenkins pipeline job
Iv'e setup a script to push to all of them one by one (with less than a second of difference between them)
**all jobs ran**

i've changed branch name bbb to aaa so now its as follows:
```
bla-service:aaa
good-service:aaa
third-service:ccc
```

Ran the script and only **two jobs ran**
**expected three jobs to run**

finally i tested with all repos with same branch name
```
bla-service:aaa
good-service:aaa
third-service:aaa
```
only one job ran
**expected three jobs to run**

the pipeline doesn't run if branch is identical on the web hook request, even if the repository is different (when time difference between requests if up to 3 seconds)

this looks like a bug
tested on 1.5.10