OF-1028: Synchronized block scope should be minimal.

To reduce the chance of lock contention, locks should only be put
in effect when the code accesses data that is sensitive to concurrent
access.

src/java/org/jivesoftware/openfire/streammanagement/StreamManager.java

@@ -134,9 +134,9 @@ public class StreamManager {
 	 */
 	public void processClientAcknowledgement(Element ack) {
 		if(isEnabled()) {
-			synchronized (this) {
-				if (ack.attribute("h") != null) {
-					long count = Long.valueOf(ack.attributeValue("h"));
+			if (ack.attribute("h") != null) {
+				long count = Long.valueOf(ack.attributeValue("h"));
+				synchronized (this) {
 					// Remove stanzas from temporary storage as now acknowledged
 					Log.debug("Ack: h={} mine={} length={}", count, clientProcessedStanzas, unacknowledgedServerStanzas.size());
 					if (count < clientProcessedStanzas) {