Expose AStatsSocket_close() from the statsd apex

As part of statsd becoming a Mainline module in R, we need to formalize
the statsd APIs called from outside the statsd apex.

Bug: 145923416
Test: m
Change-Id: I296a018cc93d95bda77d95f8161acbbe983a5d51
diff --git a/libstats/socket/libstatssocket.map.txt b/libstats/socket/libstatssocket.map.txt
index e2e7ae3..5c13904 100644
--- a/libstats/socket/libstatssocket.map.txt
+++ b/libstats/socket/libstatssocket.map.txt
@@ -14,6 +14,7 @@
         AStatsEvent_writeAttributionChain; # apex # introduced=30
         AStatsEvent_addBoolAnnotation; # apex # introduced=30
         AStatsEvent_addInt32Annotation; # apex # introduced=30
+        AStatsSocket_close; # apex # introduced=30
     local:
         *;
 };