Servo Node should listen to the monitored planning scene topic

[amalnanavati]

The servo node allows us to pass in a parameter specifying where the primary planning scene monitor will publish updates, so its planning scene can also be updated. (code here). We do not currently use that parameter, but should

Note that the above change does not address the issue where the Servo node doesn't account for Octomap collisions, see moveit2#2548.

[amalnanavati]

Closed with #33