Fix for IOFSwitch/OFSwitchImpl leak

- Fix for ONOS-1765

- OFSwitchImpl.java
   Changes TLS bufffer map to WeakHashMap to eliminate buffer for
   eliminated switches.
- OFMessageDamper.java
   Added a hack to remove cached entries related to disconnected switch
- TimedCache.java
   Backdoor acccess to manually invalidate cached entries
- FlowProgrammer.java
   Propagate removeSwitch event
    FlowPusher -> OFMessageDamper to invalidate cache.
- FlowPusher.java
   Switched `assignedQueues` to concurrent version of WeakHashMap
- PlanInstallRuntime.java
   Changed FlowModCount map to WeakHashMap and removed
   strong reference to IOFSwitch

Change-Id: Idb5014379ebc5658d0ae58ebcdbb2bf03e981df7
diff --git a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowProgrammer.java b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowProgrammer.java
index 838533d..046d130 100644
--- a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowProgrammer.java
+++ b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowProgrammer.java
@@ -128,6 +128,7 @@
             synchronizer.interrupt(sw);
         }
         pusher.deleteQueue(sw, true);
+        pusher.invalidate(sw);
     }
 
     @Override
diff --git a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java
index 98c2f97..37e1b44 100644
--- a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java
+++ b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java
@@ -70,6 +70,8 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import com.google.common.cache.CacheBuilder;
+
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 
 /**
@@ -299,8 +301,11 @@
      * Main thread that reads messages from queues and sends them to switches.
      */
     private class FlowPusherThread extends Thread {
+        // Weak ConncurrentHashMap
         private Map<IOFSwitch, SwitchQueue> assignedQueues
-                = new ConcurrentHashMap<IOFSwitch, SwitchQueue>();
+                = CacheBuilder.newBuilder()
+                    .weakKeys()
+                    .<IOFSwitch, SwitchQueue>build().asMap();
 
         final Lock queuingLock = new ReentrantLock();
         final Condition messagePushed = queuingLock.newCondition();
@@ -612,6 +617,17 @@
         }
     }
 
+    /**
+     * Invalidate.
+     *
+     * @param sw switch
+     *
+     * @see OFMessageDamper#invalidate(IOFSwitch)
+     */
+    public void invalidate(IOFSwitch sw) {
+        messageDamper.invalidate(sw);
+    }
+
     @Override
     public boolean add(IOFSwitch sw, OFMessage msg) {
         return add(sw, msg, MsgPriority.NORMAL);
diff --git a/src/main/java/net/onrc/onos/core/intent/runtime/PlanInstallRuntime.java b/src/main/java/net/onrc/onos/core/intent/runtime/PlanInstallRuntime.java
index bd332ac..f942fa8 100644
--- a/src/main/java/net/onrc/onos/core/intent/runtime/PlanInstallRuntime.java
+++ b/src/main/java/net/onrc/onos/core/intent/runtime/PlanInstallRuntime.java
@@ -1,11 +1,12 @@
 package net.onrc.onos.core.intent.runtime;
 
+import java.lang.ref.WeakReference;
 import java.util.ArrayList;
-import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.WeakHashMap;
 import java.util.concurrent.ExecutionException;
 
 import net.floodlightcontroller.core.IFloodlightProviderService;
@@ -50,7 +51,7 @@
      * TODO: This class should be wrapped into a more generic debugging framework when available.
      */
     private static class FlowModCount {
-        IOFSwitch sw;
+        WeakReference<IOFSwitch> sw;
         long modFlows = 0;
         long delFlows = 0;
         long errors = 0;
@@ -61,7 +62,7 @@
          * @param sw the switch for FlowMod statistics collection
          */
         FlowModCount(IOFSwitch sw) {
-            this.sw = sw;
+            this.sw = new WeakReference<>(sw);
         }
 
         /**
@@ -92,10 +93,12 @@
          */
         @Override
         public String toString() {
-            return "sw:" + sw.getStringId() + ": modify " + modFlows + " delete " + delFlows + " error " + errors;
+            final IOFSwitch swTemp = sw.get();
+            return "sw:" + ((swTemp == null) ? "disconnected" : swTemp.getStringId())
+                    + ": modify " + modFlows + " delete " + delFlows + " error " + errors;
         }
 
-        static Map<IOFSwitch, FlowModCount> map = new HashMap<>();
+        static Map<IOFSwitch, FlowModCount> map = new WeakHashMap<>();
 
         /**
          * This function is used for collecting statistics information. It should be called for