MAGETWO-44730: Integration Tests Failing on Travis CI

- reducing db-prefix to less then 5

Author: mazhalai

dev/tests/integration/etc/install-config-mysql.travis.php.dist

@@ -9,7 +9,7 @@ return [
     'db-user' => 'travis',
     'db-password' => '',
     'db-name' => 'magento_integration_tests',
-    'db-prefix' => 'travis_',
+    'db-prefix' => 'trv_',
     'backend-frontname' => 'backend',
     'admin-user' => \Magento\TestFramework\Bootstrap::ADMIN_NAME,
     'admin-password' => \Magento\TestFramework\Bootstrap::ADMIN_PASSWORD,