updated test cases for port 4 (index 3) i2c support.

Currently Port 4 I2C support only works partially due to the use
of Open Drain configuration for the I2C Data Line.

Some sensors (tested with HT Compass Sensor) works fine.
The LEGO NXT Ultrasound sensor does not work in this configuration.

A proper fix is to modify the I2C drivers to support Push-Pull
configuration where the I2C Data Line switches between Input and
Output configuration where necessary.