ksmbd: common: use struct_group_attr instead of struct_group for network_open_info

4byte padding cause the connection issue with the applications of MacOS.
smb2_close response size increases by 4 bytes by padding, And the smb
client of MacOS check it and stop the connection. This patch use
struct_group_attr instead of struct_group for network_open_info to use
 __packed to avoid padding.

Fixes: 0015eb6e

 ("smb: client, common: fix fortify warnings")
Cc: stable@vger.kernel.org
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>