We cannot be in PS mode when running PLT tests, so we need to make sure we're
in active mode.  Also, we need to clear up the rx_counter when we stop PLT,
otherwise it could cause problems when entering PLT again.

Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Reviewed-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>