D14724: autotests: don't fail if an unrelated window shows up.

[David Faure]

dfaure added reviewers: broulik, davidedmundson.

REPOSITORY
  R242 Plasma Framework (Library)

REVISION DETAIL
  https://phabricator.kde.org/D14724

To: dfaure, hein, drosca, broulik, davidedmundson
Cc: kde-frameworks-devel, #plasma, michaelh, ngraham, bruns