BUG: Missing Modified() call

While reviewing differences between the bounded and unbounded
itkLBFGSOptimizer.cxx
itkLBFGSBOptimizer.cxx

The missing call to "Modified()" was identified.

Change-Id: I0bd0526a047fab3f8cb79d4a5b35c81385bd3b0f
Merge topic 'AddExplicitModifiedCall'

9ba4fd98 BUG: Missing Modified() call