nss_ldap currently has a file dependency on /%{_lib}/security/pam_ldap.so, which makes yum depsolver download the whole filelists database for upgrades. Please replace the file dependency with a dependency on pam_ldap package instead. See the following link for more information why file dependencies outside of /etc, /bin, /sbin, /usr/bin, or /usr/sbin directories are considered undesirable: http://fedoraproject.org/wiki/PackagingGuidelines#File_Dependencies
*** This bug has been marked as a duplicate of bug 601931 ***