Correction of rebuild on comment on wrong pipeline

[Turiok]

filtered jenkins jobs with SCMSource of the payload on comment trigger

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close #256

Be careful with this PR. There isn't a lot of code but the fix seems very important I think.
If several people can test it, It'll be appreciated.

In GitLabMergeRequestCommentTrigger class to find which job build depending on the payload information of the webhook. There isn't link between GItlab Project Id and Jenkins jobs. I add a if between these 2 objects with the job parent Item.

# Verify the projectId is asked
if (gitLabSCMSource.getProjectId() == getPayload().getMergeRequest().getTargetProjectId()
    && isTrustedMember(gitLabSCMSource, sourceContext.getOnlyTrustedMembersCanTrigger())) {
    # search in all jobs of the same owner.  And there isn't another verification with the payload
    for (Job<?, ?> job : owner.getAllJobs()) {

To reproduce the previous problem :

• Create 2 Gitlab projects with the same Owner.
• Each project with a MR with the same branch name.
• Configure webhook settings for Jenkins in GItlab project settings and enable comment event
• In Jenkins create 2 multibranches pipelines and enable comment rebuild trait
• On first MR add the comment to launch a webhook.
• Verify the right pipeline is executed
• On second MR add the comment to launch a webhook.
• The pipeline executed is the same that the first one.

Be careful to test it with any other pipeline executed.

[Turiok]

With this for, we loop to all jobs. Even out of the projectId. And there isn't more check after with the payload

[Turiok]

I try to check the link between the source of the payload and the job in the for.

I don't know if there is a better solution

[Turiok]

With this break, only one job can be executed.

I'm wondering if it is possible to have 2 multi branch pipelines with the same project?
Because if it can, this break stop the wake up of the second pipeline in case of comment

[jetersen]

Seems safer way of handling it.