### Describe the issue

Restarting bitcoin, mempool starts filling from scratch.

### Can you reliably reproduce the issue?
#### If so, please list the steps to reproduce below:
1. Wait for mempool to reach for example 3000 transactions
2. Restart bitcoin
3. Watch mempool filling slowly from scratch

### Expected behaviour
Mempool would already contain ~3000 TX on startup

### Actual behaviour
It starts at 0 and fills up slowly with a few per second.

### Screenshots.
http://imgur.com/a/or82d

### What version of bitcoin-core are you using?
Windows x64 0.14rc1 binary from https://bitcoin.org/bin/bitcoin-core-0.14.0/test.rc1/


### Any extra information that might be useful in the debugging process.
I may not be aware of how the mempool.dat thing works and there could just be a misunderstanding.

{
            const COutPoint &prevout = tx.vin[i].prevout;
            const CCoins *coins = inputs.AccessCoins(prevout.hash);
            assert(coins);
            
            if (coins->IsCoinBase()) {
                if (nSpendHeight - coins->nHeight < COINBASE_MATURITY)
                    return state.Invalid(false,
                        REJECT_INVALID, "bad-txns-premature-spend-of-coinbase",
                        strprintf("tried to spend coinbase at depth %d", nSpendHeight - coins->nHeight));
            }
            
            nValueIn += coins->vout[prevout.n].nValue;
            if (!MoneyRange(coins->vout[prevout.n].nValue) || !MoneyRange(nValueIn))
                return state.DoS(100, false, REJECT_INVALID, "bad-txns-inputvalues-outofrange");
        }
        if (nValueIn < tx.GetValueOut())
            return state.DoS(100, false, REJECT_INVALID, "bad-txns-in-belowout", false,
                strprintf("value in (%s) < value out (%s)", FormatMoney(nValueIn), FormatMoney(tx.GetValueOut())));
        
        CAmount nTxFee = nValueIn - tx.GetValueOut();
        if (nTxFee < 0)
            return state.DoS(100, false, REJECT_INVALID, "bad-txns-fee-negative");
        nFees += nTxFee;
        if (!MoneyRange(nFees))
            return state.DoS(100, false, REJECT_INVALID, "bad-txns-fee-outofrange");
    return true;
}
}
bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks)