Remove unnecessary use of logstash::indexer from subunit_worker

Previously the subunit2sql worker.pp was including the
logstash::indexer class, but this was really only done for the
/etc/logstash dir which is where the worker puts all it's files. This
commit corrects this by just ensuring the directory exists instead of
importing the other class which includes a lot of other unnecessary
things.

Change-Id: I3f00d1bb443ee0f1b2a8e9d393f46a7e9ebf148a
Merge "Remove unnecessary use of logstash::indexer from subunit_worker"