Make autoblocks update with the parent block

Change SpecialBlock so that when a block already exists, it just updates
the existing block rather than deleting and inserting a new row. Also,
Block::update() was changed to update existing autoblocks with the new
block parameters.

Bug: 48813
Change-Id: I5403f6e1d7f8f07273cd5da8068b928fdddcdfc9
Merge "Make autoblocks update with the parent block"