Errors in from mating plugin in stdout

[bsb808]

This was initially brought up during testing of PR #189.

When the joint is locked/unlocked an error message is generated in the terminal window:

[Msg] m_to_f_socket-m_to_f_plug joint locked!
Error [Param.cc:457] Out of range. Unable to set value [6.94416e-310 ] for key[upper].
Error [Param.cc:457] Out of range. Unable to set value [6.94416e-310 ] for key[lower].
[Msg] m_to_f_socket-m_to_f_plug joint unlocked!

It does not appear to affect functionality, but needs to be run to ground. At the very least it needs to be documented in the appropriate wiki(s) (e.g., https://field-robotics-lab.github.io/dave.doc/contents/manipulator_demos/Electrical-Plug-Mating-Plugin/) as a known issue so it does not surprise users. To edit the documentation, use this repo: https://github.com/Field-Robotics-Lab/dave.doc

Typically it is best to not have Error messages in the terminal as it leave users confused and unsure if things are working properly.