RM-5837 Only assert the return code if we're not expecting a failure.

rm-automation/rm-automation-community-rest-api/src/main/java/org/alfresco/rest/core/v0/BaseAPI.java

@@ -408,7 +408,10 @@ public abstract class BaseAPI
         try
         {
             HttpResponse httpResponse = doRequestJson(HttpPost.class, requestUrl, adminUser, adminPassword, requestParams);
+            if (!expectFailure)
+            {
                 assertEquals("POST request was not successful.", httpResponse.getStatusLine().getStatusCode(), 200);
+            }
             return httpResponse;
         }
         catch (InstantiationException | IllegalAccessException error)