DfsInserter#openStream: Suppress resource warning about DfsReader

DfsReader is not opened in a try-with-resource because in the case where
the method returns an ObjectStream.Filter, the DfsReader should only be
closed from within the Filter's close() method.

Suppress the resource warning.

Change-Id: Ifcaf5e4a326bd1d03c6331b476c645ca43943b34
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsInserter.java

@@ -669,6 +669,7 @@ public class DfsInserter extends ObjectInserter {
 
 		@Override
 		public ObjectStream openStream() throws IOException {
+			@SuppressWarnings("resource") // Explicitly closed below
 			final DfsReader ctx = db.newReader();
 			if (srcPack != packKey) {
 				try {