Fix multiple notifications for 1 subcription on comments

Clients receive multiple notifications (3 mails) per comment created when the server is configured with a specific contribution.

Expected Result: only 1 notification mail per comment created

How to reproduce:

• Take a hotfixed 10.10 instance with JSF installed
• Add to the configuration an SMTP emulator (e.g. FakeSMTP), start it and target it by Nuxeo
• Add the attached contribution in nxserver/config
• Boot Nuxeo
• Ensure in the_admin_console that the comments are using the Current state: Comments stored under the commented document (Unsure whether this is a required step)
• create a Workspace in JSF and for this worskpace, in the manage_>_alerts_tab, create a subscription for user Administrator on New Comment
• Create a Note document in this folder
• Add a comment to the Note, and notice in the SMTP emulator that 3 pieces of mail are sent by Nuxeo

• (Unsubscribe in the Workspace Administrator from the New Comment alert, then when adding a comment to the Note, no mail is sent at all)