puller cache clearing

+ add adb command to manually clear puller cache
+ try to clear puller cache every 10s

Test: manual test
Change-Id: I8005cacd189de1880fcaeb030efbe21e6d3c0244
diff --git a/cmds/statsd/src/guardrail/StatsdStats.h b/cmds/statsd/src/guardrail/StatsdStats.h
index 1f4bfa6..f254327 100644
--- a/cmds/statsd/src/guardrail/StatsdStats.h
+++ b/cmds/statsd/src/guardrail/StatsdStats.h
@@ -85,6 +85,9 @@
     // Maximum size of all files that can be written to stats directory on disk.
     static const int kMaxFileSize = 50 * 1024 * 1024;
 
+    // How long to try to clear puller cache from last time
+    static const long kPullerCacheClearIntervalSec = 1;
+
     /**
      * Report a new config has been received and report the static stats about the config.
      *