Move HardFork DB update to BlockchainDB::add_block()

Ensures the database is consistent.

Also simplifes blockchain_import in that verify mode off has less to
work around.

src/blockchain_db/blockchain_db.cpp

@@ -130,6 +130,7 @@ uint64_t BlockchainDB::add_block( const block& blk
   // DB's new height based on this added block is only incremented after this
   // function returns, so height() here returns the new previous height.
   uint64_t prev_height = height();
+  m_hardfork->add(blk, prev_height);
 
   block_txn_stop();
 

src/blockchain_utilities/blockchain_import.cpp

@@ -469,9 +469,6 @@ int import_from_file(FakeCore& simple_core, const std::string& import_file_path,
           try
           {
             simple_core.add_block(b, block_size, cumulative_difficulty, coins_generated, txs);
-            #if !defined(BLOCKCHAIN_DB) || (BLOCKCHAIN_DB == DB_LMDB)
-            simple_core.m_hardfork->add(b, h-1);
-            #endif
           }
           catch (const std::exception& e)
           {

src/cryptonote_core/blockchain.cpp

@@ -2692,9 +2692,6 @@ bool Blockchain::handle_block_to_main_chain(const block& bl, const crypto::hash&
 
   TIME_MEASURE_FINISH(addblock);
 
-  // this will not fail since check succeeded above
-  m_hardfork->add(bl, new_height - 1);
-
   // do this after updating the hard fork state since the size limit may change due to fork
   update_next_cumulative_size_limit();