learning-switch: Make test-controller work with OpenFlow 1.3+.

learning-switch: Make test-controller work with OpenFlow 1.3+.

The controller setup in my personal test environment has been broken for a
while.  I figured that it wasn't anything important, though, because no one
else had reported similar problems.  Anyway, it turns out that enabling
OpenFlow 1.3 by default broke test-controller because OpenFlow 1.3 doesn't
send table misses to the controller by default.  This commit fixes the
problem.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Alex Wang <alexw@nicira.com>