This switches the default behavior of S3A output streams
to warning that Syncable.hsync() or hflush() have been
called; it's not considered an error unless the defaults
are overridden.
This avoids breaking applications which call the APIs,
at the risk of people trying to use S3 as a safe store
of streamed data (HBase WALs, audit logs etc).
Contributed by Steve Loughran.
Change-Id: I0a02ec1e622343619f147f94158c18928a73a885
a68671eaf7