_feedapi_parse() doesn't pass settings to _feedapi_call_parsers()

This is related to #559242: settings not passed to secondary parsers.

Not sure what has happened in the past with the parameters for _feedapi_call_parsers(). The third parameter is supposed to be $settings, but instead we call it with $feed->half_done ? FALSE : TRUE.

Here's a patch according to my understanding. It works with my secondary parser, along with the other patch from #559242: settings not passed to secondary parsers.