wp_login_form() uses the incorrect scheme

[mdawaffe]

wp_login_form() currently uses the 'login' auth scheme, which only serves HTTPS requests when force_ssl_admin() is set.

The correct scheme for the form is 'login_post', which serves HTTPS requests when either force_ssl_login() or force_ssl_admin is set.

Attached.

[nacin]

In [18444]:

Use login_post context for wp_login_form action. props mdawaffe, see #18137 for trunk.

[nacin]

In [18463]:

Use login_post context for wp_login_form action. props mdawaffe, fixes #18137. for the 3.2 branch.