Fix request actions in user registration's local listing

• Install user registration addon
• Configure addon to display local listing
• Give Everything right to a user on a workspace (e.g.: user manager on niark)
• Invite a user to this workspace
• As an admin, approve request
• As the invited user, finalize your account creation
• As the workspace manager, go to local invitations listing and try to delete the invitation

=> an error appears saying the invitation can't be deleted
=> Logs show the following warning:

14:42:37,135 WARN  [UserRegistrationActions] Unable to delete user request:Privilege 'Read' is not granted to 'manager'

=> method isDocumentDeletable() in UserRegistrationActions bean ( https://github.com/nuxeo/nuxeo-platform-user-registration/blob/master/nuxeo-platform-user-registration-web/src/main/java/org/nuxeo/ecm/user/registration/actions/UserRegistrationActions.java ) should not only check the document's state but also if current user has the proper permissions on the document.
=> Same for the other actions (revive, validate...).