Can you try:

rpmbuild --rebuild --without servers <src_rpm>

(automatically means --without zfs --without ldiskfs
..........

Wrote: rpmbuild/RPMS/x86_64/lustre-client-2.5.1-2.6.32_431.11.2.el6.x86_64.x86_64.rpm
Wrote: rpmbuild/RPMS/x86_64/lustre-client-modules-2.5.1-2.6.32_431.11.2.el6.x86_64.x86_64.rpm
Wrote: rpmbuild/RPMS/x86_64/lustre-client-source-2.5.1-2.6.32_431.11.2.el6.x86_64.x86_64.rpm
Wrote: rpmbuild/RPMS/x86_64/lustre-client-tests-2.5.1-2.6.32_431.11.2.el6.x86_64.x86_64.rpm
Wrote: rpmbuild/RPMS/x86_64/lustre-iokit-2.5.1-2.6.32_431.11.2.el6.x86_64.x86_64.rpm
Wrote: rpmbuild/RPMS/x86_64/lustre-client-debuginfo-2.5.1-2.6.32_431.11.2.el6.x86_64.x86_64.rpm