MAGETWO-51862: API-Functional: Automate test to create API Request to access other customer data using customer token.

- Updated function to retrieve customer token.
- Marked test as Rest Only.
- Removed unused library.

Author: Tanniru, Murali(mtanniru)

dev/tests/api-functional/testsuite/Magento/Customer/Api/CustomerRepositoryTest.php

@@ -14,7 +14,6 @@
 use Magento\TestFramework\TestCase\WebapiAbstract;
 use Magento\Framework\Webapi\Exception as HTTPExceptionCodes;
 use Magento\Framework\Exception\NoSuchEntityException;
-use Symfony\Component\Config\Definition\Exception\Exception;
 
 /**
  * Test class for Magento\Customer\Api\CustomerRepositoryInterface