fix tests

Author: kolea2

google-cloud-datastore/src/test/java/com/google/cloud/datastore/it/StatementExecutor.java

@@ -54,7 +54,6 @@ final void execute(Tuple<String, Statement>... tuples) throws Exception {
     for (Tuple<String, Statement> tuple : tuples) {
       String groupId = tuple.x();
       Statement statement = tuple.y();
-      Thread.sleep(10000);
       Future<?> future = executorService.submit(statement::execute);
       try {
         // waiting for statement to execute
@@ -83,7 +82,7 @@ private boolean transactionConflict(Exception exception) {
         && exception.getCause().getClass() == DatastoreException.class
         && exception
             .getMessage()
-            .contains("contention"); // exception raise coz of optimistic concurrency
+            .contains("Conflict"); // exception raise coz of optimistic concurrency
   }
 
   interface Statement {