libtracker-miner: Detach early the processed file in TrackerFileNotifier
libtracker-miner: Detach early the processed file in TrackerFileNotifier

This is so priv->pending_index_roots can be prepended/appended without confusing
ongoing crawling on the current folder.

hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker