Upgrade packet requests to use flow objectives API.

Addressed a few issues found while using the flow objectives across a cluster:
 * Flow objectives should be installable from any node, not just the master.
   Therefore we need to ensure all nodes initialize a driver for each switch.
 * We no longer store a list of objectives that are waiting for the switch
   to arrive. If the we don't know about the switch yet we'll try a few times
   over a few seconds to find it, but after that we'll give up and report an
   error to the client.
 * Default drivers need to be available when the FlowObjectiveManager starts
   up, otherwise it is common to get flow objective requests before any
   drivers have been loaded.

Change-Id: I1c2ea6a223232402c31e8139729e4b6251ab8b0f
diff --git a/core/api/src/main/java/org/onosproject/net/driver/DefaultDriverProviderService.java b/core/api/src/main/java/org/onosproject/net/driver/DefaultDriverProviderService.java
new file mode 100644
index 0000000..2b7eeff
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/driver/DefaultDriverProviderService.java
@@ -0,0 +1,23 @@
+/*
+ * Copyright 2015 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.driver;
+
+/**
+ * Service capable of providing a set of default drivers.
+ */
+public interface DefaultDriverProviderService extends DriverProvider {
+}