parameters passed through feature file cannot take effect

[yunxuo]

Describe the bug
when given multi description for step as below code

@given('a user with username')
@given(parsers.parse('a user with username {username}'))
@given(parsers.parse('a user with username {username} and password {password}'))
def create_user(user, username="defaultuser", password='defaultpassword'):
    user['username'] = username
    user['password'] = password

Scenario Outline: User login
    Given a user with username <username> and password <password>
    When the user logs in with username <username> and password <password>
    Then the login should be <result>

    Examples:
      | username | password    | result  |
      | testuser | password123 | success |

Parameters username, password parameters passed through feature file cannot take effect.
The default values in def are always used。

see also:
#610 pr fix this problems
#512