fix condition to not skip FastRTPS to FastRTPS pub/sub tests

[dirk-thomas]

Fix regression from #322.

Before: https://ci.ros2.org/job/ci_windows/7438/testReport/(root)/test_communication/
After: https://ci.ros2.org/job/ci_windows/7439/testReport/(root)/test_communication/

[wjwwood]

I think the logic makes sense as-is with the EQUAL, but in this scenario (XOR?) I'd expect (A OR B) AND NOT (A AND B).

[dirk-thomas]

The XOR can be expresses as NOT "${rmw1_isFastRTPS}" STREQUAL "{$rmw2_isFastRTPS}. Done in 5ce5f12.

Just using NOT rmw1_isFastRTPS EQUAL rmw2_isFastRTPS doesn't work - that is why the STREQUAL workaround is used in other places already: e.g.

system_tests/test_communication/CMakeLists.txt

Line 190 in f1771f4

NOT "${rmw_implementation1_is_opensplice}" STREQUAL "${rmw_implementation2_is_opensplice}"

The additional condition (rmw_implementation1_is_fastrtps OR rmw_implementation2_is_fastrtps) is redundant and can be removed.

[dirk-thomas]

This current patch successfully re-enables the FastRTPS-to-FastRTPS tests: see https://ci.ros2.org/job/ci_windows/7441/ (the build failed since it also uses ros2/test_interface_files#8).

[dirk-thomas]

With the tests enabled the build fails (https://ci.ros2.org/job/ci_windows/7441/) due to a bug in launch: ros2/launch#280.