JETTY-1214 dont invalidate when already invalid

git-svn-id: svn+ssh://dev.eclipse.org/svnroot/rt/org.eclipse.jetty/jetty/trunk@1568 7e9141cc-0065-0410-87d8-b60c137991c4

VERSION.txt

@@ -17,6 +17,7 @@ jetty-7.1.0-SNAPSHOT
  + JETTY-1200 SSL NIO Endpoint wraps non NIO buffers
  + JETTY-1202 Use platform default algorithm for SecureRandom
  + JETTY-1212 handle long content lengths
+ + JETTY-1214 avoid ISE when scavenging invalid session
  + Fix jetty-plus.xml reference to addLifeCycle
  + Add AnnotationConfiguration to jetty-plus.xml
  + 310467 Allow SocketConnector to create generic Connection objects

jetty-server/src/main/java/org/eclipse/jetty/server/session/AbstractSessionManager.java

@@ -1010,10 +1010,13 @@ public abstract class AbstractSessionManager extends AbstractLifeCycle implement
             // Notify listeners and unbind values
             synchronized (this)
             {
-                if (_requests<=0)
-                    doInvalidate();
-                else
-                    _doInvalidate=true;
+                if (!_invalid)
+                {
+                    if (_requests<=0)
+                        doInvalidate();
+                    else
+                        _doInvalidate=true;
+                }
             }
         }