COMP: fix unused result warning in ProcessObject

This patch fixes the following warning:

ITK/Modules/Core/Common/src/itkProcessObject.cxx:797:67: warning:
expression result unused [-Wunused-value]
  m_Inputs.insert( DataObjectPointerMap::value_type(name, NULL) ).first;

Change-Id: Idc5d4c9368a02b52ef5bf5ad0071ead00b2504c4
Merge topic 'FixProcessObjectUnusedResultWarning'

643dd16 COMP: fix unused result warning in ProcessObject