Implement host probing retry with major refactoring

- Implement probe retry
- Switch to typical core/provider design pattern for HostProbingService
  and as a result decoupling the dependency between SR and HostLocationProvider

Change-Id: I33a15af580677ea376b421ac3e26f9821dcca844
diff --git a/core/api/src/main/java/org/onosproject/net/host/HostProbe.java b/core/api/src/main/java/org/onosproject/net/host/HostProbe.java
new file mode 100644
index 0000000..7303a3d
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/host/HostProbe.java
@@ -0,0 +1,58 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * 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.host;
+
+import org.onlab.packet.MacAddress;
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.Host;
+
+/**
+ * Information related to the host being probed.
+ */
+public interface HostProbe extends Host {
+    /**
+     * Gets connect point of this entry.
+     *
+     * @return connect point
+     */
+    ConnectPoint connectPoint();
+
+    /**
+     * Gets retry counter of this entry.
+     *
+     * @return retry
+     */
+    int retry();
+
+    /**
+     * Decrease retry counter of this entry by one.
+     */
+    void decreaseRetry();
+
+    /**
+     * Gets mode of this entry.
+     *
+     * @return mode
+     */
+    ProbeMode mode();
+
+    /**
+     * Gets probe MAC of this entry.
+     *
+     * @return probe mac
+     */
+    MacAddress probeMac();
+}