* Netconf lock/unlock behaviour changed to adhere to RFC 6241

* Changed commit lock error tag from "lock denied" to "in-use".
  * Changed unlock error message from "lock is already held" to #lock not active" or "lock held by other session".
  * Fixed [lock candidate succeeded even though it is modified #110](https://github.com/clicon/clixon/issues/110)

apps/backend/backend_main.c

@@ -871,6 +871,8 @@ main(int    argc,
     /* Initiate the shared candidate. */
     if (xmldb_copy(h, "running", "candidate") < 0)
 	goto done;
+    xmldb_modified_set(h, "candidate", 0);
+    
     /* Set startup status */
     if (clicon_startup_status_set(h, status) < 0)
 	goto done;