Fixes:
1) Adding "setup_standby_ports_on_rand_unselected_tor" fixture to setup
   ports in standby mode in case of active-active topology. This is
   needed for packets not to go out of unexpected tor and cause test
   failures.
2) Test is performing "config_reload", this can cause switchover (active
   to standy and viceversa). But rand_selected_dut should be in active
   state for traffic verification to pass, so after config_reload we
   need to toggle ports to rand_selected_dut.