CIFS: set signing flag in SMB2+ TreeConnect if needed

cifs_enable_signing() already sets server->sign according to what the
server requires/offers and what mount options allows/forbids, so use
that.

this is required for IPC tcon that connects to signing-required servers.
Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Acked-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/smb2pdu.c

@@ -1168,8 +1168,8 @@ SMB2_tcon(const unsigned int xid, struct cifs_ses *ses, const char *tree,
 
 		/* since no tcon, smb2_init can not do this, so do here */
 		req->hdr.sync_hdr.SessionId = ses->Suid;
-		/* if (ses->server->sec_mode & SECMODE_SIGN_REQUIRED)
-			req->hdr.Flags |= SMB2_FLAGS_SIGNED; */
+		if (ses->server->sign)
+			req->hdr.sync_hdr.Flags |= SMB2_FLAGS_SIGNED;
 	} else if (encryption_required(tcon))
 		flags |= CIFS_TRANSFORM_REQ;