Use changed LDAP structure field sequence

[dataclouder]

Addresses Issue #672 (again!) with changed field sequence in LDAP configuration.

In addition to failing with invalid LDAP configuration, the update also fails when using group_back_link_identifier, which was not in the right position in go-vcloud-director types. This change picks the right field sequence.

Test for compatibility:

go test -tags functional -run 'TestAccVcdOrgLdap|TestAccVcdOrgGroup' -v -timeout 0

Test for this specific issue:

1. apply the script from this issue comment: (change the LDAP server IP or hostname).
2. remove terraform state file
3. remove or comment out from the script the resource vcd_org_ldap.dummy
4. run terraform import vcd_org.dummy dummy
5. Change the org description and run terraform apply
6. check in the UI that the LDAP configuration persists, and that you can import groups.