Linux aarch64 get_node_names is flaky

[clalancette]

We've seen that the get_node_names test on Fast-RTPS has been flaky for a while. One example from last night's Linux aarch64 build https://ci.ros2.org/view/nightly/job/nightly_linux-aarch64_repeated/470/:

-- run_test.py: extra environment variables:
 - RMW_IMPLEMENTATION=rmw_fastrtps_cpp
-- run_test.py: extra environment variables to append:
 - LD_LIBRARY_PATH+=/home/rosbuild/ci_scripts/ws/build/rcl
-- run_test.py: invoking following command in '/home/rosbuild/ci_scripts/ws/src/ros2/rcl/rcl':
 - /home/rosbuild/ci_scripts/ws/build/rcl/test/test_get_node_names__rmw_fastrtps_cpp --gtest_output=xml:/home/rosbuild/ci_scripts/ws/build/rcl/test_results/rcl/test_get_node_names__rmw_fastrtps_cpp.gtest.xml
Running main() from gtest_main.cc
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from TestGetNodeNames__rmw_fastrtps_cpp
[ RUN      ] TestGetNodeNames__rmw_fastrtps_cpp.test_rcl_get_node_names
/home/rosbuild/ci_scripts/ws/src/ros2/rcl/rcl/test/rcl/test_get_node_names.cpp:77: Failure
Expected equality of these values:
  size_t(2)
    Which is: 2
  node_names.size
    Which is: 3
[test_rcl_get_node_names]: Found node names:
node1
my_node
node2

/home/rosbuild/ci_scripts/ws/src/ros2/rcl/rcl/test/rcl/test_get_node_names.cpp:79: Failure
Expected equality of these values:
  0
  strcmp(node2_name, node_names.data[1])
    Which is: 61
[  FAILED  ] TestGetNodeNames__rmw_fastrtps_cpp.test_rcl_get_node_names (1028 ms)
[----------] 1 test from TestGetNodeNames__rmw_fastrtps_cpp (1028 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (1028 ms total)
[  PASSED  ] 0 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] TestGetNodeNames__rmw_fastrtps_cpp.test_rcl_get_node_names

[dhood]

addressed by ros2/ci#204