Correct address for Lithuanian z39.50

According to IRSpy
http://irspy.indexdata.com/full.html?id=Z39.50%3Az39.lnb.lt%3A211%2FLNBKAT
the correct server for the National Library is z39.lnb.lt while
z39.libis.lt is the Lithuanian Union Catalogue.

BUG: 404743
FIXED-IN: 3.1.5