Given:
overlay "syncprov" not found
with the availability of
/usr/lib/ldap/syncprov-2.4.so.2 /usr/lib/ldap/syncprov-2.4.so.2.0.3 /usr/lib/ldap/syncprov.la /usr/lib/ldap/syncprov.so
you likely want "modulepath /usr/lib/ldap" and "modulepath syncprov" in your configuration.