[CIFS] Do not send tree disconnect if session is already disconnected

Noticed this when tree connect timed out (due to Samba server crash) -
we try to send a tree disconnect for a tid that does not exist
since we don't have a valid tree id yet. This checks that the
session is valid before sending the tree disconnect to handle
this case.

Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/cifssmb.c

@@ -729,7 +729,7 @@ CIFSSMBTDis(const int xid, struct cifsTconInfo *tcon)
 	 * the tcon is no longer on the list, so no need to take lock before
 	 * checking this.
 	 */
-	if (tcon->need_reconnect)
+	if ((tcon->need_reconnect) || (tcon->ses->need_reconnect))
 		return 0;
 
 	rc = small_smb_init(SMB_COM_TREE_DISCONNECT, 0, tcon,