ROS 2: clear queue on reset

[EdoardoRomiti]

We observed a possible bug of the Cartesian Interface on ROS2, when prematurely stopping a plugin whose subscribed to the /reference topic which is actively published; this is the pipeline:

• Start plugin
• Start reference broacasting
• Stop plugin
• Stop reference broacasting
• Start plugin again

It seems in this case the old reference is still in the queue and processed by the plugin. Further details here: https://github.com/ADVRHumanoids/cartesian-impedance-controller/issues/3

@JVALPASS @liesrock @alaurenzi @torydebra

[alaurenzi]

This looks solved by using the spin_all API for the main CartesIO ROS node, which requires creating an executor
@EdoardoRomiti can you push the fix? Thanks!

[EdoardoRomiti]

Done with commit 10040e1 !