### 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.

pindexNewTip = chainActive.Tip();
            pindexFork = chainActive.FindFork(pindexOldTip);
            fInitialDownload = IsInitialBlockDownload();
            
            } 
            
            for (const auto& pair : connectTrace.blocksConnected) {
                assert(pair.second);
                const CBlock& block = *(pair.second);
                for (unsigned int i = 0; i < block.vtx.size(); i++)
                    GetMainSignals().SyncTransaction(*block.vtx[i], pair.first, i);
            }
        }
        
        
        
        GetMainSignals().UpdatedBlockTip(pindexNewTip, pindexFork, fInitialDownload);
        
        if (pindexFork != pindexNewTip) {
            uiInterface.NotifyBlockTip(fInitialDownload, pindexNewTip);
        }
    } while (pindexNewTip != pindexMostWork);
    CheckBlockIndex(chainparams.GetConsensus());
    
    if (!FlushStateToDisk(state, FLUSH_STATE_PERIODIC)) {
        return false;
    }
    return true;
}
bool PreciousBlock(CValidationState& state, const CChainParams& params, CBlockIndex *pindex)