compare singletons by identity not equality (closes #16712)

Patch from Serhiy Storchaka.
diff --git a/Lib/test/test_ftplib.py b/Lib/test/test_ftplib.py
index 7028f46..299a146 100644
--- a/Lib/test/test_ftplib.py
+++ b/Lib/test/test_ftplib.py
@@ -342,7 +342,7 @@
                 # http://www.mail-archive.com/openssl-users@openssl.org/msg60710.html
                 pass
             self._ssl_closing = False
-            if getattr(self, '_ccc', False) == False:
+            if getattr(self, '_ccc', False) is False:
                 super(SSLConnection, self).close()
             else:
                 pass