ONOS-5691 ONOS-5742 Fixing intent framework difficulties

- Refactoring AbstractAccumulator to use less blocking synchronization
- Fixing bug in AbstractAccumulator that could leave some items
  without firing
- Updated IntentStore for resubmitting pending operations

Change-Id: Iaf240da65e11ceb7d7d745cf4e25bfb8c26ed1eb
diff --git a/core/net/src/main/java/org/onosproject/net/intent/impl/phase/Skipped.java b/core/net/src/main/java/org/onosproject/net/intent/impl/phase/Skipped.java
new file mode 100644
index 0000000..a8afde6
--- /dev/null
+++ b/core/net/src/main/java/org/onosproject/net/intent/impl/phase/Skipped.java
@@ -0,0 +1,48 @@
+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.intent.impl.phase;
+
+import org.onosproject.net.intent.IntentData;
+
+/**
+ * Represents a phase where an intent is not compiled.
+ * <p>
+ * This should be used if a new version of the intent will immediately override
+ * this one.
+ * </p>
+ */
+public final class Skipped extends FinalIntentProcessPhase {
+
+    private static final Skipped SINGLETON = new Skipped();
+
+    /**
+     * Returns a shared skipped phase.
+     *
+     * @return skipped phase
+     */
+    public static Skipped getPhase() {
+        return SINGLETON;
+    }
+
+    // Prevent object construction; use getPhase()
+    private Skipped() {
+    }
+
+    @Override
+    public IntentData data() {
+        return null;
+    }
+}