[1578] more fix about MEM_SUPER_STOP

src/lib/datasrc/datasrc_messages.mes

@@ -376,10 +376,12 @@ Some resource types are singletons -- only one is allowed in a domain
 % DATASRC_MEM_SUCCESS query for '%1/%2' successful
 Debug information. The requested record was found.
 
-% DATASRC_MEM_SUPER_STOP stopped at subdomain of '%1', meaning it's empty
-Debug information. The search stopped at a superdomain of the requested
-domain. The domain is an empty nonterminal, therefore it is treated  as NXRRSET
-case (eg. the domain exists, but it doesn't have the requested record type).
+% DATASRC_MEM_SUPER_STOP stopped as '%1' is superdomain of a zone node, meaning it's empty
+Debug information. The search stopped because the requested domain was
+detected to be a superdomain of some existing node of zone (while there
+was no exact match).  This means that the domain is an empty nonterminal,
+therefore it is treated  as NXRRSET case (eg. the domain exists, but it
+doesn't have the requested record type).
 
 % DATASRC_MEM_SWAP swapping contents of two zone representations ('%1' and '%2')
 Debug information. The contents of two in-memory zones are being exchanged.