[cell-centered implicit] fix bug introduced by r13823

It was not such a good idea to change the name of the protected
evalDirichletSegment_ function of the CCLocalResidual, since it can be
overwritten in derived LocalResiduals, and in fact is already
overwritten in MPNCLocalResidual. The name is changed back to its
original.



git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@13824 2fb0f335-1f38-0410-981e-8018bf24f1b0