ncg, lbfgs, tn: create test for poblano_linesearch warning

[dmdunla]

In each of these methods, there is a check on the result of poblano_linesearch:

    if (lsinfo ~= 1) && strcmp(params.Results.Display, 'iter')
        fprintf(1,[mfilename,': line search warning = %d\n'],lsinfo);
    end

There are no tests for this case. A function should be identified where this case is executed.