timers: callback useless, remove timer completely.

Change-Id: I904a91b38d846841e24149f897962abb429878be
Reviewed-on: https://gerrit.libreoffice.org/13062
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>