Drop lifecycle state to unconfigured if reading data fails

[urfeex]

Feature summary

Currently, when reading data from (or writing data to) the robot fails, we don't return a failure from read / write. We should do that.

This should reflect the request made in UniversalRobots/Universal_Robots_ROS_Driver#103

Related issues

ROS 1 issue: UniversalRobots/Universal_Robots_ROS_Driver#103

Tasks

To complete this issue involves

• Implement the feature
• Make documentation
• Make Unit test
• Make example
• Test on real hardware