[PendingFileQueueTest] Verify create + delete do not emit extra events

Summary:
When a file has been deleted, a modified event should never be emitted.

This mimics the following real behavior:

1. touch testfile; touch testfile; sleep 5; rm testfile

Verifies the changes from D21709 (second part)

Depends on D21807

Test Plan: ctest -R pendingfilequeue

Reviewers: Baloo, ngraham, astippich, poboiko

Reviewed By: Baloo, ngraham

Subscribers: kde-frameworks-devel

Tags: Frameworks, Baloo

Differential Revision: https://phabricator.kde.org/D21809