Nahum Admoni, who was originally meant to head the committee of investigation into the government's management of the war in Lebanon, decided Thursday night to leave the commission altogether. Since the committee is intended to investigate the defense establishment's role in the war, Admoni and former justice Eliahu Winograd, who replaced Admoni as head of the committee, nominated Maj.-Gen. (res.) Dr. Haim Nadel as the latest member. The Winograd commission is set to receive government approval on Sunday.