s3-rpc_server remove per-element copies of auth_session_info

s3-rpc_server remove per-element copies of auth_session_info

This is not required any more now that they are the same structure,
and shows the value in having a common structure across the codebase.

In particular, now any additional state that needs to be added to the
auth_session_info will be transparently available across the named
pipe proxy, without a need to modify the mapping layer.

Andrew Bartlett

Signed-off-by: Andrew Tridgell <tridge@samba.org>