webadmin: fixed truncation of 'until' column in tasks

'until' column in the task tree was too small for certain
locales. Doubled the size.

Change-Id: I0c6189fd65494c163a1569460aa12baf10367ce1
Bug-Url: https://bugzilla.redhat.com/1000934
Signed-off-by: Greg Sheremeta <gshereme@redhat.com>