No output from parameter events demo nodes on Fast-RTPS

[hidmic]

Bug report

Required Info:

• Operating System:
  • Ubuntu 18.04 LTS Bionic Beaver
• Installation type:
  • From source
• Version or commit hash:
  • Latest master @ d2a934b.
• DDS implementation:
  • Fast-RTPS
• Client library (if applicable):
  • rclcpp

Steps to reproduce issue

Run any of the parameter event demos. For instance,

ros2 run demo_nodes_cpp parameter_events

Expected behavior

Process terminates gracefully after the following output:

[INFO] [parameter_events]:
Parameter event:
 new parameters:
  foo
 changed parameters:
 deleted parameters:

[INFO] [parameter_events]:
Parameter event:
 new parameters:
  bar
 changed parameters:
 deleted parameters:

[INFO] [parameter_events]:
Parameter event:
 new parameters:
  baz
 changed parameters:
 deleted parameters:

[INFO] [parameter_events]:
Parameter event:
 new parameters:
  foobar
 changed parameters:
 deleted parameters:

[INFO] [parameter_events]:
Parameter event:
 new parameters:
 changed parameters:
  foo
 deleted parameters:

[INFO] [parameter_events]:
Parameter event:
 new parameters:
 changed parameters:
  bar
 deleted parameters:

[INFO] [parameter_events]:
Parameter event:
 new parameters:
 changed parameters:
  baz
 deleted parameters:

[INFO] [parameter_events]:
Parameter event:
 new parameters:
 changed parameters:
  foobar
 deleted parameters:

[INFO] [parameter_events]:
Parameter event:
 new parameters:
 changed parameters:
  foo
 deleted parameters:

[INFO] [parameter_events]:
Parameter event:
 new parameters:
 changed parameters:
  bar
 deleted parameters:

Actual behavior

Process terminates gracefully but immediately and with no output.

Additional information

Likely a timing issue, it was patched on #318 by adding artificial delays here and here but that's not a real solution.