add conditioning to get_parameter_value method import

[saikishor]

@christophfroehlich reported that the controller_manager spawner tests failed due to an import error when running tests in Humble.

• ros2/rclpy@3053a8a The get_parameter_value is available from version 3.6.o. I wanted to use the __version__ attribute to condition it, but unfortunately the rclpy doesn't have this attribute, so I went with the catch the import error and using the old library for compatibility

The following fix should solve the issue and make the spawner compatible with the older versions.

I've tested this fix by compiling and running all the tests of ros2_control with #1422, ros2_controllers with ros-controls/ros2_controllers#1071, and gazebo_ros2_control in Humble. All the tests are successful now.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.89%. Comparing base (ff3177b) to head (0eb5594).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1428   +/-   ##
=======================================
  Coverage   75.89%   75.89%           
=======================================
  Files          41       41           
  Lines        3352     3352           
  Branches     1926     1926           
=======================================
  Hits         2544     2544           
- Misses        417      418    +1     
+ Partials      391      390    -1     

Flag	Coverage Δ
unittests	75.89% <ø> (ø)

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see 1 file with indirect coverage changes

[christophfroehlich]

Thanks for fixing this!
I tested it with https://github.com/ros-controls/ros2_control_ci/actions/runs/8154134944/job/22286909088?pr=30
Now only the gz tests fail.

[olivier-stasse]

LGTM