smb: client: make smb2_compound_op() return resp buffer on success

If @out_iov and @out_buftype are passed, then return compounded
responses regardless whether the request failed or not.  This will be
useful for detecting reparse points on SMB2_CREATE responses as
specified in MS-SMB2 2.2.14.

No functional changes.

Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>