Fix for issue #108: only if both parts of traj relay are running is 'motion possible'

This updates the conditions that need to be `true` before the *motion possible* field of the `robot_status` message is set to `true`: runtime status of the `ros` and `ros_relay` programs is now taken into account.

This should not introduce any incompatibilities.

Tested both in simulation and on a real R-30iA, HandlingTool, V7.70.