fixed non-idempotent tests (#757)

docs-core/src/test/java/com/sismics/docs/core/dao/jpa/TestJpa.java

@@ -29,5 +29,9 @@ public class TestJpa extends BaseTransactionalTest {
 
         // Authenticate using the database
         Assert.assertNotNull(new InternalAuthenticationHandler().authenticate("testJpa", "12345678"));
+
+        // Delete the created user
+        userDao.delete("testJpa", user.getId());
+        TransactionUtil.commit();
     }
 }