Use renamed AStatsSocket_close()

As part of statsd becoming a Mainline module in R, we need to formalize
the API surface for statsd. This change updates the usages of
stats_log_close() to AStatsSocket_close() created in ag/10299810.

Bug: 145923416
Test: m
Change-Id: Id6a8efff657eafc349db621f39de40311863c6a1