Some bugfixes

* Fix switch state-machine bug. Need to set the state before calling
  sendRoleReqest because sendRoleRequest could directly set the role
  to Master if the switch is known to not support Nicira role requests
* In REST handling: replace empty roleChangeDescription with none so we
  don't violate IFloodlightProvider.setRole's contract of requiring a
  non-null description
* Use correct package name for FloodightProvider in
  bigfloodlight.properties