gh-155332: Use self.Value instead of bare Value in two threads-only pool tests

Author: Talen400

Lib/test/_test_multiprocessing.py

@@ -3165,7 +3165,7 @@ def test_imap_and_imap_unordered_when_buffer_is_full(self, method_name):
 
         processes = 4
         p = self.Pool(processes)
-        last_produced_task_arg = Value("i")
+        last_produced_task_arg = self.Value("i", 0)
 
         def produce_args():
             for arg in itertools.count(1):
@@ -3202,7 +3202,7 @@ def test_imap_and_imap_unordered_with_buffersize_when_buffer_is_full(
 
         processes = 4
         p = self.Pool(processes)
-        last_produced_task_arg = Value("i")
+        last_produced_task_arg = self.Value("i", 0)
 
         def produce_args():
             for arg in itertools.count(1):