Stricter options checking breaks nist.cc

Fix the breakage!

Change-Id: Ic263852cd7c8a9615d8d3dab43c6cf7d81fc8d40

examples/nist.cc

diff --git a/examples/nist.cc b/examples/nist.cc
index b29b285..607561a 100644
--- a/examples/nist.cc
+++ b/examples/nist.cc
@@ -92,7 +92,7 @@
               "cgnr");
 DEFINE_string(preconditioner, "jacobi", "Options are: "
               "identity, jacobi");
-DEFINE_string(line_search, "armijo",
+DEFINE_string(line_search, "wolfe",
               "Line search algorithm to use, choices are: armijo and wolfe.");
 DEFINE_string(line_search_direction, "lbfgs",
               "Line search direction algorithm to use, choices: lbfgs, bfgs");