Fix name of FT sensors in FT sensor orientation test in ergocub-model-test.cpp

[traversaro]

#158 silently changed the name of the FT sensors, i.e.:

• ergocub-software <= 0.3.3 names : l_arm_ft_sensor, r_arm_ft_sensor, l_leg_ft_sensor, l_foot_front_ft_sensor, l_foot_rear_ft_sensor, r_leg_ft_sensor, r_foot_front_ft_sensor, r_foot_rear_ft_sensor
• ergocub-software >= 0.3.4 names : l_arm_ft, r_arm_ft, l_leg_ft, l_foot_front_ft, l_foot_rear_ft, r_leg_ft, r_foot_front_ft, r_foot_rear_ft

However, the names used in the ergocub-model-test.cpp were not updated. However, the tests were silently skipped due to the following logic, that skipped a test if a sensor was not present:

    // Depending on the ergocub model, the sensor could be absent
    if (!comp.model().isFrameNameUsed(sensorName))
    {
        return true;
    }

[Nicogene]

Nice catch!