When importing a watch-only address over `importmulti` with a specific timestamp, the wallet's `nTimeFirstKey` will be set to 1.
I think we should add a optional timestamp to `CWallet::AddWatchOnly()` and use it when importing addresses or pubkeys.

return false;
                }
            }
        }
        MilliSleep(100);
    }
    return false;
}
CKeyPool::CKeyPool()
{
    nTime = GetTime();
}
CKeyPool::CKeyPool(const CPubKey& vchPubKeyIn)
{
    nTime = GetTime();
    vchPubKey = vchPubKeyIn;
}
CWalletKey::CWalletKey(int64_t nExpires)
{
    nTimeCreated = (nExpires ? GetTime() : 0);
    nTimeExpires = nExpires;
}
void CMerkleTx::SetMerkleBranch(const CBlockIndex* pindex, int posInBlock)
{
    
    hashBlock = pindex->GetBlockHash();
    
    nIndex = posInBlock;
}
int CMerkleTx::GetDepthInMainChain(const CBlockIndex* &pindexRet) const