cifs: use tcon allocation functions even for dummy tcon

In smb2_reconnect_server, we allocate a dummy tcon for
calling reconnect for just the session. This should be
allocated using tconInfoAlloc, and not kmalloc.

Fixes: 3663c904 ("cifs: check reconnects for channels of active tcons too")
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>