This patch ensures that the "FLUSH" command will write the updates out to

This patch ensures that the "FLUSH" command will write the updates out to
RRD before returning to the user.  Before, it returned when the update was
"dequeued"; updates were not necessarily on disk.

Also, for new nodes, the cache_lock is not held while we are setting up
the new node.  We don't want to be holding the lock if the stat() blocks.
--  kevin brintnal

git-svn-id: svn://svn.oetiker.ch/rrdtool/trunk/program@1527 a5681a0c-68f1-0310-ab6d-d61299d08faa