optimize table locking of segment meta table in termtagger import

Currently the TermTaggerImport locks a bunch of tables to get the next segments which are to be tagged.
This could be improved by doing the following steps:

1. Instead of creating the segment meta entries only for the selected X segments we could create all segment meta entries for all segments of the Task in a first step (insert into LEK_segment_meta values select segmentId, taskGuid from LEK_segments where taskGuid = ?; Add a duplicate key update (or better ignore if possible) statement to the insert).
2. refactor the getNextSegmentSelect so that it does a "select for update" call which hopefully locks the affected rows then.
3. refactor the later foreach meta->save() to one update statement which sets the state for all segmentIds in (the above fetched ones)