Revert "Revert "Exclude roundtrip definition import cases from mixed version runs""

This reverts commit 9c5314f.

Author: michaelklishin

deps/rabbit/test/definition_import_SUITE.erl

@@ -178,15 +178,27 @@ import_case16(Config) ->
     end.
 
 export_import_round_trip_case1(Config) ->
-    %% case 6 has runtime parameters that do not depend on any plugins
-    import_file_case(Config, "case6"),
-    Defs = export(Config),
-    import_raw(Config, rabbit_json:encode(Defs)).
+    case rabbit_ct_helpers:is_mixed_versions() of
+      false ->
+        %% case 6 has runtime parameters that do not depend on any plugins
+        import_file_case(Config, "case6"),
+        Defs = export(Config),
+        import_raw(Config, rabbit_json:encode(Defs));
+      _ ->
+        %% skip the test in mixed version mode
+        {skip, "Should not run in mixed version environments"}
+    end.
 
 export_import_round_trip_case2(Config) ->
-    import_file_case(Config, "case9", "case9a"),
-    Defs = export(Config),
-    import_parsed(Config, Defs).
+    case rabbit_ct_helpers:is_mixed_versions() of
+      false ->
+        import_file_case(Config, "case9", "case9a"),
+        Defs = export(Config),
+        import_parsed(Config, Defs);
+      _ ->
+        %% skip the test in mixed version mode
+        {skip, "Should not run in mixed version environments"}
+    end.
 
 import_on_a_booting_node(Config) ->
     %% see case5.json