Sitemap date not updated when an extension version is deleted

[hoangphamEclipse]

When an extension version is deleted, the last_updated_date of its extension database entry is not updated. This causes the mirror to be out-of-sync with upstream.

For example:

• Extension Ext has 2 versions ExtV0.0.1 and ExtV0.0.2. Then the last_udpated_date will be the published date of ExtV0.0.2.
• For some reason ExtV0.0.1 is deleted, but the last updated time is not changed.
• Thus, the mirror wont update the metadata on its end.

This issue causes the mirror to throw an error when its trying to remove some out-of-date extensions.