Ticket #852: CI: avoid to run 2 pipelines in case of MR
When a branch is pushed and a MR is associated, 2 pipelines are triggered 1 for the MR and 1 for the branch (jobs are duplicated in MR pipeline).
When a branch is pushed and a MR is associated, 2 pipelines are triggered 1 for the MR and 1 for the branch (jobs are duplicated in MR pipeline).