Fix _xml_get_filtered_events() to return num_events
Fix _xml_get_filtered_events() to return num_events

This method would return more the num events, and the the multi-backend
code was fixing it auto-magically.

freedesktop-unofficial-mirror/telepathy__telepathy-logger,freedesktop-unofficial-mirror/telepathy__telepathy-logger,freedesktop-unofficial-mirror/telepathy__telepathy-logger