Fix HumanLogger not working when logging just one quantity

[RiccardoGrieco]

The periodic thread (e.g. the run() function) in human logger is started inside the attachAll method.

Turns out that, since the device implements both IWrapper and IMultipleWrapper, the first one is preferred when the list of devices to attach contains only one of them (see here).

In such case, only the attach() method belonging to IWrapper is called. In our case, this happens when using the logging of only one between the kinematics and dynamics data.

This PR is to solve this issue.

[RiccardoGrieco]

cc @claudia-lat

[RiccardoGrieco]

Thanks @lrapetti, merging.