Speed up the application of robust loss functions.

Since we added special handling for the case for rho[2] < 0,
the bulk of CorrectJacobian is pointless in the common case.
So add a simple one dimensional loop which rescales the Jacobian.
This speeds up this method immensely.

The robustification of a Jacobian gets speeded up by > 50%.

Change-Id: I97c4e897ccbb5521c053e1fb931c5d0d32f542c7