Avoid directly comparing string to blob in CommentIntegrationTest

Sql Server is unable to directly compare a blob to a string without casting the string to varbinary. Core database tests do not test that blobs can be used in a condition, so this does not appear to be an expectation of databases. This test can be easily modified while maintaining test integrity by changing:

$logged = (bool) Database::getConnection()->select('watchdog')
  ->fields('watchdog', ['wid'])
  ->condition('type', 'system')
  ->condition('message', "View display '@id': Comment field formatter '@name' was disabled because it is using the comment view display '@display' (@mode) that was just disabled.")
  ->condition('variables', serialize($arguments))
  ->execute()
  ->fetchField();
$this->assertTrue($logged);

To:

$logged = Database::getConnection()->select('watchdog')
  ->fields('watchdog', ['variables'])
  ->condition('type', 'system')
  ->condition('message', "View display '@id': Comment field formatter '@name' was disabled because it is using the comment view display '@display' (@mode) that was just disabled.")
  ->execute()
  ->fetchField();
$this->assertEquals(serialize($arguments), $logged);