### 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.

CCoinsViewCache view(pcoinsTip);
        if (!DisconnectBlock(block, state, pindexDelete, view))
            return error("DisconnectTip(): DisconnectBlock %s failed", pindexDelete->GetBlockHash().ToString());
        bool flushed = view.Flush();
        assert(flushed);
    }
    LogPrint("bench", "- Disconnect block: %.2fms\n", (GetTimeMicros() - nStart) * 0.001);
    
    if (!FlushStateToDisk(state, FLUSH_STATE_IF_NEEDED))
        return false;
    if (!fBare) {
        
        std::vector<uint256> vHashUpdate;
        for (const auto& it : block.vtx) {
            const CTransaction& tx = *it;
            
            CValidationState stateDummy;
            if (tx.IsCoinBase() || !AcceptToMemoryPool(mempool, stateDummy, it, false, NULL, NULL, true)) {
                mempool.removeRecursive(tx, MemPoolRemovalReason::REORG);
            } else if (mempool.exists(tx.GetHash())) {
                vHashUpdate.push_back(tx.GetHash());
            }
        }
        
        
        
        
        
        mempool.UpdateTransactionsFromBlock(vHashUpdate);
    }