Fixed #24769 -- Cast optparse verbosity argument to an integer for better backwards compatibility.

Using `BaseCommand.options_list` makes Django use the legacy optparse
parser, which does not set the verbosity attribute correctly. Now the
verbosity argument is always cast to int. Regression in 8568638 (#19973).

Initial report and patch from blueyed.

tests/user_commands/management/commands/optparse_cmd.py

@@ -16,4 +16,5 @@ class Command(BaseCommand):
         options["example"]
         # BaseCommand default option is available
         options['verbosity']
+        assert isinstance(options['verbosity'], int), "verbosity option is not int, but %s" % type(options['verbosity'])
         self.stdout.write("All right, let's dance %s." % options["style"])