Fix MAV_CMD_IMAGE_START_CAPTURE unit test usage for take photo

FW Landing Pattern: Support for stop photo/video. Plus item unit test.

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Added param2 for start video capture (update interval)
Excluded param2 above from PX4 as it's fixed to 0.2Hz
Re-added param2 test within CameraSectionTest (start video capture)

Mavlink spec changed

Move set camera photo mode to be first item

Fixed all the bugs the new tests found