[Synchronisation][Target Path] Synchronisation failure when target path already exists

Affected version : 7.X.RELEASE, with Xsquash4jira and xsquash4gitlab

Steps to reproduce

• To be done between two synchronization cycles
• Create a new sycnhroinsation (S1) and define a target path target folder
• Fill all fields to a correctly synchronisation and click [Add]
• Create a second synchronisation and define the same target path target folder
• Fill all fields to a correctly synchronisation and click [Add]
• Wait the next sync cycle

Observed behaviour Only one of the two synchronizations is successfull, the other is Failed with error in logs.

Expected result In this case, when the both synchronisations aren't sync status, it should be to have an alerte before adding, like sync already exists.