s3-libsmbclient Convert dos error codes to NTstatus in async libsmbclient.

s3-libsmbclient Convert dos error codes to NTstatus in async libsmbclient.

DOS error codes were being lost with the conversion to async
libsmbclient.  If we're passing around NTSTATUS internally,
let's just convert it when we get it.

DOS ACCESS_DENIED on nautilus was not prompting for other credentials,
because it was not being mapped.