### 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.

CFeeRate oldFeeRate(mi->GetModifiedFee(), mi->GetTxSize());
                if (newFeeRate <= oldFeeRate)
                {
                    return state.DoS(0, false,
                            REJECT_INSUFFICIENTFEE, "insufficient fee", false,
                            strprintf("rejecting replacement %s; new feerate %s <= old feerate %s",
                                  hash.ToString(),
                                  newFeeRate.ToString(),
                                  oldFeeRate.ToString()));
                }
                BOOST_FOREACH(const CTxIn &txin, mi->GetTx().vin)
                {
                    setConflictsParents.insert(txin.prevout.hash);
                }
                nConflictingCount += mi->GetCountWithDescendants();
            }
            
            
            
            if (nConflictingCount <= maxDescendantsToVisit) {
                
                
                BOOST_FOREACH(CTxMemPool::txiter it, setIterConflicting) {