Revert "fix check style"

This reverts commit 9d18274.

Author: jakelandis

x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/execution/ExecutionService.java

@@ -78,6 +78,7 @@
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
 
 import static org.elasticsearch.xpack.core.ClientHelper.WATCHER_ORIGIN;