message: Overly verbose keypool reserve/return traces in log
  Fix issue such debug statement will be printed
  only if `debug=db` is set.
diff: @@ -2654,7 +2654,7 @@ void CWallet::ReserveKeyFromKeyPool(int64_t& nIndex, CKeyPool& keypool)
  if (!HaveKey(keypool.vchPubKey.GetID()))
  throw runtime_error("ReserveKeyFromKeyPool(): unknown key in key pool");
  assert(keypool.vchPubKey.IsValid());
  - LogPrintf("keypool reserve %d\n", nIndex);
  + LogPrint("db","keypool reserve %d\n", nIndex);
  }
  }
  @@ -2666,7 +2666,7 @@ void CWallet::KeepKey(int64_t nIndex)
  CWalletDB walletdb(strWalletFile);
  walletdb.ErasePool(nIndex);
  }
  - LogPrintf("keypool keep %d\n", nIndex);
  + LogPrint("db","keypool keep %d\n", nIndex);
  }
  void CWallet::ReturnKey(int64_t nIndex)
  @@ -2676,7 +2676,7 @@ void CWallet::ReturnKey(int64_t nIndex)
  LOCK(cs_wallet);
  setKeyPool.insert(nIndex);
  }
  - LogPrintf("keypool return %d\n", nIndex);
  + LogPrint("db","keypool return %d\n", nIndex);
  }
  bool CWallet::GetKeyFromPool(CPubKey& result)
  