Disable timestamp checking in AM/XMPP.
Disable timestamp checking in AM/XMPP.

- Timestamp checking relied on clocks being synchronized
  correctly on all machines, which we can't guarantee.
- Need to redesign this mechanism for avoiding stale
  messages somehow, or stop using the persist option...



nathansamson/OMF,phelipealves/omf,nathansamson/OMF,LABORA-UFG/omf,phelipealves/omf,nathansamson/OMF,phelipealves/omf,mytestbed/omf,mytestbed/omf,LABORA-UFG/omf,mytestbed/omf,LABORA-UFG/omf,mytestbed/omf,ardadouk/omf6,LABORA-UFG/omf,phelipealves/omf,maxott/omf6,ardadouk/omf6,nathansamson/OMF,nathansamson/OMF,nathansamson/OMF