Remove unused pox controller from the RouteFlow repo.
Change default controller to Ryu in some source files.

  * In build.sh and rftest make ryu the default controller.
  * In build.sh and rftest remove POX support.
Fix broken line being added to /etc/fstab.

Fix bug where build.sh would add a broken cgroup mount line to
/etc/fstab if run in dry-run mode.
Fix issue in build.sh when running as non-root user.
Make logging easier to read.

 * Add timestamp+module+severity to log messages.