Clean up temporary sudoedit files on success; Bug #929

This is a regression introduced in sudo 1.9.0.

src/sudo_edit.c

@@ -698,7 +698,10 @@ sudo_edit_copy_tfiles(struct command_details *command_details,
 
 	/* Overwrite the old file with the new contents. */
 	if (sudo_copy_file(tf[i].tfile, tfd, sb.st_size, tf[i].ofile, ofd,
-	    tf[i].osize) == -1) {
+		tf[i].osize) == 0) {
+	    /* success, remove temporary file. */
+	    unlink(tf[i].tfile);
+	} else {
 bad:
 	    sudo_warnx(U_("contents of edit session left in %s"), tf[i].tfile);
 	    errors++;