As you can see above, the the resolver totally ignores the fact that the samba4 packages are installed and tries to pull in the samba 3 packages. This smells like a packaging bug to me but I could be wrong.
As far as I can see there is no Samba4 libsmbclient in CentOS 6 - hence when kdebase wants libsmbclient it pulls in the Samba3 version, which has a dependency of samba-winbind-clients, which in turn has dependcies on samba-winbind and samba-common, all which conflicts with the installed Samba4 packages.
This on a CentOS6 system:
# repoquery --whatprovides libsmbclient libsmbclient-0:3.6.23-46el6_9.x86_64 libsmbclient-0:3.6.23-46el6_9.i686 libsmbclient-0:3.6.23-43.el6_9.x86_64 libsmbclient-0:3.6.23-45.el6_9.x86_64 libsmbclient-0:3.6.23-44.el6_9.i686 libsmbclient-0:3.6.23-44.el6_9.x86_64 libsmbclient-0:3.6.23-42.el6_9.i686 libsmbclient-0:3.6.23-46el6_9.x86_64 libsmbclient-0:3.6.23-41.el6.x86_64 libsmbclient-0:3.6.23-45.el6_9.i686 libsmbclient-0:3.6.23-41.el6.i686 libsmbclient-0:3.6.23-42.el6_9.x86_64 libsmbclient-0:3.6.23-46el6_9.i686 libsmbclient-0:3.6.23-43.el6_9.i686
and on a CentOS7 system:
# repoquery --whatprovides libsmbclient libsmbclient-0:4.6.2-12.el7_4.x86_64 libsmbclient-0:4.6.2-11.el7_4.x86_64 libsmbclient-0:4.6.2-10.el7_4.i686 libsmbclient-0:4.6.2-11.el7_4.i686 libsmbclient-0:4.6.2-10.el7_4.x86_64 libsmbclient-0:4.6.2-12.el7_4.i686 libsmbclient-0:4.6.2-8.el7.i686 libsmbclient-0:4.6.2-8.el7.x86_64
It doesn't look like a packaging bug, it looks like yum doing the correct thing.
P.