Optimizations for better flow setup rate.
    - avoid instanstiation of routekey for LPM find.
    - for entry create take last modified time from setup time instead of
      UTCtimestamp
    - avoid exporting flow stats as part of flow create, those will be sent
      in the next cycle of flowstatscollector.
Taking care of review comment.
Change arguments to find and get functions of patricia to be constants.
moving GetUcRoute to flow_table.cc
As per review comments.
Merge remote-tracking branch 'upstream/master'
using API GetInet4UnicastRouteTable as per review comment.
Merge pull request #192 from Prabhjot-Sethi/master

Optimizations for better flow setup rate.