Make HardFork object available to BlockchainDB and derived DB implementations

This will later allow the HardFork object's DB update functions to be
called when the DB transaction that persists across block add/remove is
open.

src/cryptonote_core/blockchain.cpp

@@ -290,6 +290,8 @@ bool Blockchain::init(BlockchainDB* db, const bool testnet, const bool fakechain
   }
   m_hardfork->init();
 
+  m_db->set_hard_fork(m_hardfork);
+
   // if the blockchain is new, add the genesis block
   // this feels kinda kludgy to do it this way, but can be looked at later.
   // TODO: add function to create and store genesis block,