gh-90369: change test server threads to joinable

These were made daemons in an otherwise unrelated commit. The test code that
joins them was not deleted and still works, so they can just be made joinable
again.

Author: duaneg

Lib/test/test_ftplib.py

@@ -283,7 +283,6 @@ class DummyFTPServer(asyncore.dispatcher, threading.Thread):
     def __init__(self, address, af=socket.AF_INET, encoding=DEFAULT_ENCODING):
         threading.Thread.__init__(self)
         asyncore.dispatcher.__init__(self)
-        self.daemon = True
         self.create_socket(af, socket.SOCK_STREAM)
         self.bind(address)
         self.listen(5)
@@ -1052,7 +1051,6 @@ def setUp(self):
         self.sock.settimeout(20)
         self.port = socket_helper.bind_port(self.sock)
         self.server_thread = threading.Thread(target=self.server)
-        self.server_thread.daemon = True
         self.server_thread.start()
         # Wait for the server to be ready.
         self.evt.wait()

Lib/test/test_poplib.py

@@ -211,7 +211,6 @@ class DummyPOP3Server(asyncore.dispatcher, threading.Thread):
     def __init__(self, address, af=socket.AF_INET):
         threading.Thread.__init__(self)
         asyncore.dispatcher.__init__(self)
-        self.daemon = True
         self.create_socket(af, socket.SOCK_STREAM)
         self.bind(address)
         self.listen(5)