ajaxPostTimeout doesn't have to be multiplied by 1000, because it is used as is on ScriptRenderer, so the client should just get the same value in both cases

(well, ajaxPostTimeout should be the same timeout + 500ms)

fixes #1617
Merge pull request #1637 from lift/diego_issue_1617

Fix an issue in ajaxPostTimeout calculation in LiftServlet that caused futures to stick around spinning longer than they should have.