Fix non-sef endpoint url generation

[danyaPostfactum]

Your plugin does not work correctly with disabled SEF links.
Url to "add" page is generated like http://site.com/?page_id=5&woo-walletadd/

Use wc_get_endpoint_url to pass a query var and generate correct url (both sef and non-sef)

[malsubrata]

@danyaPostfactum
Thanks for contributing to our GitHub repository. Yes you are right we should use wc_get_endpoint_url instead of wc_get_account_endpoint_url.