LDAP binding calls are made even if $g_login_method <> LDAP

If for some reason $g_use_ldap_email or $g_use_ldap_realname are ON with
$g_login_method <> 'LDAP', binding calls are attempted when retrieving
the user's e-mail or real name.

Adding a check on $g_login_method to avoid this unwanted behavior.

Fixes 0014442