close impressions manager on shutdown

Author: mredolatti

client/src/main/java/io/split/client/SplitFactoryImpl.java

@@ -202,6 +202,8 @@ public void run() {
                     _log.info("Successful shutdown of segment fetchers");
                     splitFetcherProvider.close();
                     _log.info("Successful shutdown of splits");
+                    impressionsManager.close();
+                    _log.info("Successful shutdown of impressions manager");
                     uncachedFireAndForget.close();
                     _log.info("Successful shutdown of metrics 1");
                     cachedFireAndForgetMetrics.close();