mod_http_admin_api: metrics: Filter out a value that is commonly nan at startup The upload bytes count is typically nan at startup, which cannot legally be encoded in JSON. I haven't assessed whether any other metrics might emit nan under other circumstances, but this fixes the most visible issue right now.

--% conflicts: mod_bookmarks
module:log("info", "mod_bookmarks has been deprecated, now loading mod_bookmarks2")
module:depends("bookmarks2")