ObjectDownloadListener#onWritePossible: Make code spec compatible
Current code violates the ServletOutputStream contract. For every
out.isReady() == true either write or close of that ServletOutputStream
should be called.
See also this issue upstream for more context: [1].
Change-Id: Ied575f3603a6be0d2dafc6c3329d685fc212c7a3 Signed-off-by: David Ostrovsky <david@ostrovsky.org> Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>