available plugin notification by mail is incorrect

Testing difficulty: HARD (requires site upgrade and DB access)

1. Install a recent 2.3 site. Make sure that cron.php IS NOT executed automatically to have control over that. Also, DO NOT click on "Check for updates" button during this test.
2. At the Site administration ► Server ► Update notifications, enable updateautocheck and updatenotifybuilds and set updateminmaturity to Alpha
3. Install the latest HotPot activity module from the Plugins directory.
4. Run cron.php
5. TEST: Make sure that no notification about the HotPot available update is sent.
6. TEST: You should get the notification about 2.4 and 2.5dev update available with no repeated line (this is to test MDL-37003).
7. Upgrade the site to the latest 2.4 patched with submitted patches (again, DO NOT click the Check for updates button during the upgrade).
8. Execute the following SQL to force re-fetching data on the next cron:

   UPDATE mdl_config_plugins SET value=1 WHERE plugin = 'core_plugin' AND name='recentfetch';

9. Run cron.php
10. TEST: Make sure you again receive no notification about the HotPot available.