fix:sentry-8669029d: fix crash on unexpected double subscription creation.
Description
A crash were reported in sentry : https://murena-sas.sentry.io/issues/7003065413/?project=4509597400170496&referrer=project-issue-stream, regarding non-catch DB constraint issue, on murena notifications subscription. This hide a concurrence issue while updating subscription list.
Fix add mutex on these subscription update task, and defensively catch the unexpected exception.e this part here. -->