Fix bug where libmv tracking incorrectly succeeds on failure

Before this patch, if Ceres returned USER_SUCCESS indicating that
Ceres was only changing the tracked quad slightly between
iterations (indicating convergence), no final correlation check
was done. This leads to incorrectly returning that the tracking
was successful, when it actually failed.



git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk@60970 954f8c5b-7b00-dc11-b283-0030488c597c