Bug: Tag#update_post_category_counts effectively called
`update_all("tag_count_general" => 123, :tag_count => 456)`, which led
to an argument error due to the :tag_count symbol being treated as a
keyword argument.
Fix: Don't mess around with `update_all`, just regenerate the tag counts
then `save!` the post. We have to do this in an after_save callback
because we need the updated category to be in the database for `set_tag_counts`
to work. Delete `fix_post_counts` because it was unused.
This is most likely a regression caused by the upgrade of the
newrelic_rpm gem to 6.12. This can only be reproduced in production when
using Newrelic and it didn't happen before the upgrade. Presumably
Newrelic is splatting the arguments when it calls `update_all`, which
causes symbol keys to be treated as keywords.
bfdc13a4bb