Reopen db connection after doing SpecialPageCacheUpdates

Reopen db connection after doing SpecialPageCacheUpdates

Special page updates on commons have been broken recently due
to Mysql "going away" after doing the ActiveUsers special page
cache update. Presumably this is because we were only repinging
the server after QueryPage updates, and not the callback updates
(Combined with a spike in wikidata recentchanges entries making
the ActiveUsers callback now take about an hour to complete)

Bug: T176055
Change-Id: Ic344940460c353544d7c08bbe2d8c900f6cc73da