Efforts to avert a bloody Senate confrontation over job-discrimination legislation appear to be coming unglued. A group of moderate Republicans led by John C. Danforth (R-Mo.) has been negotiating with civil rights advocates and the White House in a search for a compromise. So far, Danforth has offered seven versions of the legal test plaintiffs must meet to win a discrimination suit. Six versions were acceptable to civil rights groups, but the White House balked. The White House can live with the seventh, but civil rights forces reject it. Meanwhile, Attorney General Dick Thornburgh, in a six-page analysis of Danforth's efforts, says the proposal has "serious shortcomings."