winbind: directly use dcerpc_binding_handle_is_connected() in reset_connection_on_err...

winbind: directly use dcerpc_binding_handle_is_connected() in reset_connection_on_error() SAMR code

In the end we should avoid rpccli_is_connected(), rpccli_set_timeout() and the
whole rpc_pipe_client concept.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14457

Pair-Programmed-With: Stefan Metzmacher <metze@samba.org>

Signed-off-by: Ralph Boehme <slow@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Sat Aug  8 10:59:38 UTC 2020 on sn-devel-184