Implement updateMetric and getLoad methods of ControlPlaneMonitor

- Add rrd4j jar, and wrap it as a bundle for karaf
- Implement updateMetric and getLoad methods
- Add unit test for two methods
- Revise the DefaultMetricDatabase to make it generate unique in
  memory storage space
- Revise the ControlPlaneMonitor interface
- Rename percentage to ratio, due to long string unsupport
  issue in RRD

Change-Id: Ia9d56f8e4f4bcd7ef7a29732668caa9c6a885ecf
diff --git a/apps/cpman/app/pom.xml b/apps/cpman/app/pom.xml
index 78d88bf..8a3bc9a 100644
--- a/apps/cpman/app/pom.xml
+++ b/apps/cpman/app/pom.xml
@@ -108,6 +108,7 @@
             <groupId>org.rrd4j</groupId>
             <artifactId>rrd4j</artifactId>
             <version>2.2</version>
+            <scope>provided</scope>
         </dependency>
         <dependency>
             <groupId>com.sun.jersey</groupId>
@@ -184,7 +185,8 @@
                             org.onlab.rest.*,
                             org.onosproject.*,
                             org.onlab.util.*,
-                            org.jboss.netty.util.*
+                            org.jboss.netty.util.*,
+                            org.rrd4j.*
                         </Import-Package>
                         <Web-ContextPath>${web.context}</Web-ContextPath>
                     </instructions>