Add command to clear puller cache

Test: manual test
Change-Id: Id1fa48b5a6f2200d22f4a746763f65d0c8d65f72
diff --git a/cmds/statsd/src/external/StatsPuller.cpp b/cmds/statsd/src/external/StatsPuller.cpp
index cadc535..da14434 100644
--- a/cmds/statsd/src/external/StatsPuller.cpp
+++ b/cmds/statsd/src/external/StatsPuller.cpp
@@ -59,6 +59,11 @@
     return ret;
 }
 
+void StatsPuller::ClearCache() {
+    lock_guard<std::mutex> lock(mLock);
+    mCachedData.clear();
+}
+
 }  // namespace statsd
 }  // namespace os
 }  // namespace android