Prevent Race condition in media.metrics

Change scope of locking to avoid a window of vulnerability on queue
manipulation and item merging. Also cleans up a string manipulation
error exposed by the poc for the queue bug.

Bug: 68015343
Test: repeated running of PoC without crash
Change-Id: Iafa82936e6ec2e25793187e0fa17c2a23085f58f
diff --git a/media/libmediametrics/include/MediaAnalyticsItem.h b/media/libmediametrics/include/MediaAnalyticsItem.h
index dd7452f..5f9b916 100644
--- a/media/libmediametrics/include/MediaAnalyticsItem.h
+++ b/media/libmediametrics/include/MediaAnalyticsItem.h
@@ -243,7 +243,7 @@
         enum {
             kGrowProps = 10
         };
-        void growProps(int increment = kGrowProps);
+        bool growProps(int increment = kGrowProps);
         size_t findPropIndex(const char *name, size_t len);
         Prop *findProp(const char *name);
         Prop *allocateProp(const char *name);