Fix deprecation warnings when deprecated amqp.timeout overriden by it original value

There was multiple reports from developers that AMQPConnection trigger deprecation warnings, especially when phpunit tests runt with process isolation on.

After some investigation done with the help of @aeryaguzov the code that trigger error was found. PHPUnit backups and then [restore ini settings](https://github.com/sebastianbergmann/phpunit/blob/b8b1d78bf3d7d4d07777d47a36362f700ace8c12/src/Framework/TestCase.php#L822), so `amqp.timeout` are overridden by it original value, i.e. it doesn't change it value in any way.

This PR adds problem demonstration and solution.

It would be nice to have it in next path release (1.4.1).