[ONOS-4849] NETCONF function for FUJITSU OLT #6

- Add alart command for FUJITSU OLT
   volt-notification-alertfilter <netconf:target>
   volt-notification-setalertfilter <netconf:target> <alert-severity>
   volt-notification-subscribe <netconf:target> {disable}
- Update fujitsu-drivers.xml and shell-config.xml in FUJITSU directory
- Apply Yuta's and Andrea's suggestion to startSubscription method and other methods which related to startSubscription method.
  -> Remove startSubscriptionConnection() and createSubscriptionString() method in 4th patch-set.
  -> Modify cosmetic issue related to Static-string.
  -> Update "No replay" to "No reply" in VoltGetPonLinksCommand.java

Change-Id: I2c8d5484ea0ff9f0b1b970fe8b183bec12193c46
diff --git a/protocols/netconf/api/src/main/java/org/onosproject/netconf/NetconfSession.java b/protocols/netconf/api/src/main/java/org/onosproject/netconf/NetconfSession.java
index 3e35b5a..1d83fd6 100644
--- a/protocols/netconf/api/src/main/java/org/onosproject/netconf/NetconfSession.java
+++ b/protocols/netconf/api/src/main/java/org/onosproject/netconf/NetconfSession.java
@@ -16,6 +16,7 @@
 
 package org.onosproject.netconf;
 
+import com.google.common.annotations.Beta;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 
@@ -60,7 +61,7 @@
             throws NetconfException;
 
     /**
-     * Executes an RPC to the server and wrap the request in RPC header.
+     * Executes an synchronous RPC to the server and wrap the request in RPC header.
      *
      * @param request the XML containing the request to the server.
      * @return Server response or ERROR
@@ -158,6 +159,15 @@
     void startSubscription() throws NetconfException;
 
     /**
+     * Starts subscription to the device's notifications.
+     *
+     * @param filterSchema XML subtrees to indicate specific notification
+     * @throws NetconfException when there is a problem starting the subscription
+     */
+    @Beta
+    void startSubscription(String filterSchema) throws NetconfException;
+
+    /**
      * Ends subscription to the device's notifications.
      *
      * @throws NetconfException when there is a problem ending the subscription