Fix o.e.pde.unittest.junit-feature to get proper parent.

Change-Id: Iff3c7af9b186a143e0520eb4aeb9613330acaf3c
Reviewed-on: https://git.eclipse.org/r/c/pde/eclipse.pde.ui/+/192045
Tested-by: PDE Bot <pde-bot@eclipse.org>
Reviewed-by: Alexander Kurtakov <akurtako@redhat.com>