[4211] Addressed review comments.

Two nits.

doc/guide/dhcp6-srv.xml

@@ -2602,7 +2602,7 @@ should include options from the isc option space:
 
       <para>In some uncommon deployments where no stable storage is
       available, it is desired to configure the server to not try to
-      store the server identifier on the hard drive. It is controlled
+      store the server identifier on the stable storage. It is controlled
       by the value of <command>persist</command> boolean parameter:
 <screen>
 "Dhcp6": {

src/bin/dhcp6/dhcp6.spec

@@ -43,7 +43,8 @@
             "item_name": "persist",
             "item_type": "boolean",
             "item_optional": true,
-            "item_default": true
+            "item_default": true,
+            "item_description": "Indicates if generated server identifier should be stored in a stable storage."
         }
         ]
       },