Only add noDisplay activities to freeform source tasks.

We started adding noDisplay activities to source tasks to make the
resolver activity show up within the same task bounds as what caused it
to appear. However, in other cases it might cause to add a noDisplay
activity to a task in which we don't expect anything to appear, e.g.
home task when launching from home.

Bug: 26128908
Bug: 26023670
Change-Id: I2f64e82b3c3754cdbcb4cac3f907674344e67e04