Fix utf8mb4 on vendor tables

When creating the schema for test these tables use default length for
string: 255. Which fail when using utf8mb4.

> Syntax error or access violation: 1071 Specified key was too long; max key length is 767 bytes

Also move the `setKeepStaticConnections` in before and after class to
avoid:

> SAVEPOINT DOCTRINE2_SAVEPOINT_2 does not exist

See https://github.com/dmaicher/doctrine-test-bundle#troubleshooting

src/Wallabag/ApiBundle/Entity/AuthCode.php

@@ -8,6 +8,22 @@ use FOS\OAuthServerBundle\Entity\AuthCode as BaseAuthCode;
 /**
  * @ORM\Table("oauth2_auth_codes")
  * @ORM\Entity
+ * @ORM\AttributeOverrides({
+ *     @ORM\AttributeOverride(name="token",
+ *         column=@ORM\Column(
+ *             name   = "token",
+ *             type   = "string",
+ *             length = 191
+ *         )
+ *     ),
+ *     @ORM\AttributeOverride(name="scope",
+ *         column=@ORM\Column(
+ *             name   = "scope",
+ *             type   = "string",
+ *             length = 191
+ *         )
+ *     )
+ * })
  */
 class AuthCode extends BaseAuthCode
 {