Merge changes I95a821aa,I4a90a3b6,I9f77a16a

* changes:
  BUG-2078  Stats not being collected from all nodes, dangling nodes left in oper data store after mininet disconnects BUG-2049  DataStore failure in StatisticsManager
  Bug 2106: Refactored FlowCapableInventoryProvider to properly work with failures.
  Bug 2103: Revert "Bug 2101: Do not block processing on transaction submit."