smb2_ioctl: add support for FSCTL_SRV_COPYCHUNK

smb2_ioctl: add support for FSCTL_SRV_COPYCHUNK

SMB2 clients can issue FSCTL_SRV_COPYCHUNK requests in order to copy
data between files on the server side only, rather than reading data
then writing back from the client. FSCTL_SRV_COPYCHUNK is used by
default for Explorer SMB2 file copies on Windows Server 2012.

2.2.32.1 SRV_COPYCHUNK_RESPONSE in [MS-SMB2] describes the requirement
for the server to provide maximum copychunk request size limits in ioctl
responses carrying STATUS_INVALID_PARAMETER.

Reviewed by: Jeremy Allison <jra@samba.org>