Obtain tx hash and tx output index from amount and output offset

Fixes problem of obtaining incorrect outputs used for tx input.

Reverts to earlier intended behavior that was fixed in previous
commit's split of get_output_tx_and_index into two functions.

src/cryptonote_core/blockchain.cpp

@@ -170,7 +170,7 @@ bool Blockchain::scan_outputkeys_for_indexes(const txin_to_key& tx_in_to_key, vi
     try
     {
       // get tx hash and output index for output
-      auto output_index = m_db->get_output_tx_and_index_from_global(i);
+      auto output_index = m_db->get_output_tx_and_index(tx_in_to_key.amount, i);
 
       // get tx that output is from
       auto tx = m_db->get_tx(output_index.first);