[nemo-qml-plugin-calendar] Fix calendar event tests

Recent changes to NemoCalendarEventQuery requires that test code
wait for query results, which may not be available immediatedly.
Merge pull request #39 from pgerdt/fix-event-tests

Fix calendar event tests
Merge pull request #40 from pvuorela/master

[nemo-qml-plugin-calendar] Allow to get agenda model data by row index
[nemo-qml-plugin-calendar] Support setting recurrence end date for events