test_in_tail: Make sure to clean up pos file

In addition, show a message when fails to remove temp files.

Signed-off-by: Takuro Ashie <ashie@clear-code.com>

test/plugin/test_in_tail.rb

@@ -34,8 +34,9 @@ def cleanup_directory(path)
       Dir.glob("*", base: path).each do |name|
         begin
           cleanup_file(File.join(path, name))
-        rescue
+        rescue => e
           # expect test driver block release already owned file handle.
+          puts "Failed to clean up #{File.join(path, name)}: #{e}"
         end
       end
     else
@@ -978,6 +979,7 @@ def test_rotate_file_with_write_old_and_no_new_file(data)
     end
 
     def sub_test_rotate_file(config = nil, expect_emits: nil, expect_records: nil, timeout: 5)
+      File.open("#{TMP_DIR}/tail.pos", "wb") { |f| }
       file = Fluent::FileWrapper.open("#{TMP_DIR}/tail.txt", "wb")
       file.puts "test1"
       file.puts "test2"