s3:winbind: Refactor append_afs_token(), do not take winbindd_response struct as...

s3:winbind: Refactor append_afs_token(), do not take winbindd_response struct as parameter

Refactor the append_afs_token() function to do not take a
winbindd_response as a parameter but its members directly. The AFS token
is returned as an out parameter in a DATA_BLOB, and the caller is
responsible for setting it the extra_data winbindd_response field and
extending the winbindd_response length.

Later winbindd_dual_pam_auth() will be converted to a local RPC
call handler and the netr_Validation will be returned in the 'r' struct
from the child to the parent. The parent will then fill the
winbindd_response struct.

Signed-off-by: Samuel Cabrero <scabrero@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>