Update the db2 probe guide

Idea created by iulian_ursu Employee on Oct 19, 2016

    When trying to activate the db2 probe it fails and the output of the commands './db2_monitor' and 'ldd db2_monitor' ran in the db2 probe directory points towards a missing library:
    './db2_monitor: error while loading shared libraries: libdb2.so.1: cannot open shared object file: No such file or directory'

    This library is located away from the other libraries. Therefore, the path to its location need to be added in the robot controller for the probe to activate.

    It is necessary that this info is added somewhere in the probe guide (i.e. troubleshooting section). It would avoid unnecessary delays in the probe implementation.

    Many thanks.