fix  a memory leak.

This fixes
 warning: Potential leak of memory pointed to by 'only' [clang-analyzer-unix.Malloc]

Bug: None
Test: The warning is gone.
Change-Id: I596f422c2409241a47aba381c35da0a874f38c59
diff --git a/services/mediaanalytics/MediaAnalyticsService.cpp b/services/mediaanalytics/MediaAnalyticsService.cpp
index 876c685..f3bb35c 100644
--- a/services/mediaanalytics/MediaAnalyticsService.cpp
+++ b/services/mediaanalytics/MediaAnalyticsService.cpp
@@ -404,6 +404,8 @@
     } else {
         dumpRecent(result, ts_since, only);
     }
+    free((void*)only);
+    only=NULL;
 
 
     if (clear) {