web: behaviour: fix scroll to id
web: behaviour: fix scroll to id

Scroll based on the offset of the parent (since getElement gives us
absolute position). Offset that further by `scrollToIdPadding` so logs
don't appear right at the top of the screen (hidden behind the step
name).

Signed-off-by: Aidan Oldershaw <30ef7a6e0d016bc846f26d89dacbd23aceded206@pivotal.io>

concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse