Flush the bufwriter before syncing the underlying writer
Flush the bufwriter before syncing the underlying writer

If the data isn't flushed to the underlying implementation, then syncing
will not really help.

Signed-off-by: mulhern <7b51bcf507bcd7afb72bf8663752c0ddbeb517f6@redhat.com>

stratis-storage/stratisd,stratis-storage/stratisd,stratis-storage/stratisd