Revert DNS cache flush command deletion from "Cleanup: Delete dead code."

This reverts part of commit 1604e18615f824adb2d54c36320069ba6fcb4796.
The DNS cache flushing code needs to be called when routes change.

Change-Id: I20d39eabfa088deeeeeff0c3292b1910fd948b0d
bug:16549455
3 files changed
tree: a379b52b3b615df5de87be16c099cd69ed1717a9
  1. client/
  2. include/
  3. server/