Traits on WebTestBase cause PHP Fatal error in php 5.6

Problem/Motivation

When updating the acquia_contenthub module, we found that running our test suite against 5.6.32 and below caused php fatal errors. Test output below.

The crux of the issue is use statements for traits contain the same name as the traits in WebTestBase namespace. Not sure why this doesn't fail in php7, but so far its only in php 5.6

$ php core/scripts/run-tests.sh --php /home/travis/.phpenv/shims/php --verbose --url http://localhost:8080 acquia_contenthub
Drupal test run
---------------
Tests to be run:
  - Drupal\acquia_contenthub\Tests\FieldClearingNodeTest
  - Drupal\acquia_contenthub\Tests\IntegrationTest
  - Drupal\acquia_contenthub\Tests\NodeFormTest
  - Drupal\acquia_contenthub\Tests\ParagraphsTest
  - Drupal\acquia_contenthub\Tests\TaxonomyTermTest
  - Drupal\Tests\acquia_contenthub\Unit\ContentHubEntitiesTrackingTest
  - Drupal\Tests\acquia_contenthub\Unit\ContentHubEntityDependencyTest
  - Drupal\Tests\acquia_contenthub\Unit\ContentHubEntityEmbedHandlerTest
  - Drupal\Tests\acquia_contenthub\Unit\Controller\ContentHubExportQueueControllerTest
  - Drupal\Tests\acquia_contenthub\Unit\Controller\ContentHubReindexTest
  - Drupal\Tests\acquia_contenthub\Unit\Encoder\ContentHubCdfEncoderTest
  - Drupal\Tests\acquia_contenthub\Unit\EntityManagerTest
  - Drupal\Tests\acquia_contenthub\Unit\Form\NodeFormTest
  - Drupal\Tests\acquia_contenthub\Unit\Form\NodeTypePreviewImageFormTest
  - Drupal\Tests\acquia_contenthub\Unit\ImportEntityManagerTest
  - Drupal\Tests\acquia_contenthub\Unit\Normalizer\ContentEntityNormalizerTest
  - Drupal\Tests\acquia_contenthub\Unit\Normalizer\ContentEntityViewModesExtractorTest
  - Drupal\Tests\acquia_contenthub\Unit\Plugin\QueueWorker\ContentHubImportQueueBaseTest
  - Drupal\Tests\acquia_contenthub\Unit\QueueItem\ImportQueueItemTest
  - Drupal\Tests\acquia_contenthub\Unit\Session\ContentHubUserSessionTest
Test run started:
  Friday, March 2, 2018 - 06:09
Test summary
------------
Drupal\acquia_contenthub\Tests\FieldClearingNodeTest          45 passes             1 exceptions   9 messages
PHP Fatal error:  Cannot use Drupal\Tests\node\Traits\ContentTypeCreationTrait as ContentTypeCreationTrait because the name is already in use in /home/travis/build/drupal/docroot/core/modules/simpletest/src/WebTestBase.php on line 22
Fatal error: Cannot use Drupal\Tests\node\Traits\ContentTypeCreationTrait as ContentTypeCreationTrait because the name is already in use in /home/travis/build/drupal/docroot/core/modules/simpletest/src/WebTestBase.php on line 22

Proposed resolution

Rename the remaining traits so they don't conflict.

Remaining tasks

User interface changes

None.

API changes

None.

Data model changes

None.