Fix robot connection check

[ggorjup]

Hello, this PR fixes the robot connection check in ABB hardware interface (as mentioned in #78 (comment)).

Bug

Currently, the loop counter is incremented before comparing it to NUM_CONNECTION_RETRIES. The counter can therefore never be equal to NUM_CONNECTION_RETRIES within the loop, so the following check can never be true:

    if (counter == NUM_CONNECTION_TRIES)
    {
      RCLCPP_ERROR(LOGGER, "Failed to connect to robot");
      return CallbackReturn::ERROR;
    }

This means that even if robot connection fails, the hardware interface falsely reports a successful activation.

Bugfix

By switching to post-increment, we ensure that counter == NUM_CONNECTION_RETRIES in the final loop and the activation error is raised if robot connection fails.

Test

We can test this by running the following command without the robot or simulator connected, and waiting for the timeout:
ros2 launch abb_bringup abb_control.launch.py description_package:=abb_irb1200_support description_file:=irb1200_5_90.xacro launch_rviz:=false use_fake_hardware:=false configure_via_rws:=false

Without this bugfix, the driver reports successful activation of robot hardware and controllers after connection timeout.
With this bugfix, the driver raises a hardware activation error.

[Yadunund]

Thanks for the fix.