r6165: fixed up the userinfo composite code. Fixes include:

r6165: fixed up the userinfo composite code. Fixes include:

- talloc should always be done in the right context. For example, when creating
  the userinfo_state structure, place it inside the composite
  structure, not directly on the pipe. If this isn't done then
  correct cleanup can't happen on errors (as cleanup destroys the top
  level composite context only)

- define private structures like userinfo_state in the userinfo.c
  code, not in the public header

- only keep the parameters we need in the state structure. For
  example, the domain_handle is only needed in the first call, so we
  don't need to keep it around in the state structure, but the level is
  needed in later calls, so we need to keep it

- always initialise [out,ref] parameters in RPC calls. The [ref] part
  means that the call assumes the pointer it has been given is
  valid. If you don't initialise it then you will get a segv on
  recv. This is why the code was dying.

- don't use internal strucrure elements like the pipe
  pipe->conn->pending outside of the internal rpc implementation. That
  is an internal list, trying to use it from external code will cause crashes.

- rpc calls assume that rpc call strucrures remain valid for the
  duration of the call. This means you need to keep the structures
  (such as "struct samr_Close") in the userinfo_state strucrure,
  otherwise it will go out of scope during the async processing

- need to remember to change c->state to SMBCLI_REQUEST_DONE when the
  request has finished in the close handler, otherwise it will loop
  forever trying to close

Mimir, please look at the diff carefully for more detailed info on the fixes