Controlboard unit test failing on MacOs

[xela-95]

The unit test developed in #86 revealed a potential error in how mutexes are managed in the plugins, as revealed in the unit test failing in the github CI for MacOs (see #86 (comment)).

In fact, this bug could be affecting all the plugins, not only the controlboard one, since the way in which they implement the singleton is the same.

[xela-95]

Actually this is happening also for ConfigurationParsingTest. See https://github.com/robotology/gz-sim-yarp-plugins/actions/runs/8263726863/job/22605783707