Fixed a bug in the symmetricom driver when there is no timing card.

The symmetricom driver had an invalid constant applied to correct for
leap seconds.  The output was wrong by 4s.

It looks like we added this code in 2011 and did not update it.

We need to have something that can update itself off of a gps leapsecond
table.

git-svn-id: https://redoubt.ligo-wa.caltech.edu/svn/advLigoRTS/trunk@4446 6dcd42c9-f523-4c6d-aada-af552506706e