[WIP] PHP-1107: Additional connection timeout fixes

https://jira.mongodb.org/browse/PHP-1107
@derickr: I didn't quite follow the comment: "Move this to within the loop & use real timeout setting". Is this because `select(2)` is documented as possibly modifying the timeout argument (it mentions `pselect(2)` differs in that it doesn't do so, although it takes a different struct for timeout). If so, I'm all for ensuring we initialize `tval` properly during each loop iteration.