[core] Improved m_FreshLoss and m_pRcvLossList in processData()

[gou4shi1]

This PR consists two commits:

• Moved m_FreshLoss.push_back() out of the incoming loop.
  Previously, m_FreshLoss.push_back() happened inside

  for (vector<CUnit *>::iterator unitIt = incoming.begin(); unitIt != incoming.end(); ++unitIt)
  

  result that srt_loss_seqs will be added and logged repeatedly.

• Also protected m_pRcvLossList->insert() with m_RcvBufferLock.

  • Update m_FreshLoss and m_pRcvLossList at the same time to improve their consistency and reduce one m_RcvLossLock.
  • Fix the synchronous issue between processData() and tsbpd(), related PR [core] make sure data to be inserted into CRcvLossList are monotonic #2195, I found that the error logs of that PR happened frequently when the workload is high.