s3/rpc_server: don't unmarshall PDUs twice

s3/rpc_server: don't unmarshall PDUs twice

DCE/RPC PDUs are currently unmarshalled firstly by the generic librpc
dcerpc_read_ncacn_packet_[send/recv] functions, and subsequently a
second time by the source3 rpc_server, which ignores the unmarshalled
packet and re-parses the receive buffer.

Signed-off-by: David Disseldorp <ddiss@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Wed Dec 11 22:24:31 CET 2013 on sn-devel-104