Netconf monitoring RFC 6022 Sessions (https://github.com/clicon/clixon/issues/370)

- statistics and transport/source-host parameters
  - extended internal NETCONF hello with transport and source-host attributes
clixon-lib,yang
  - Moved all extended internal NETCONF attributes to the clicon-lib namespace
C-API:
  - wrapped most attribute creation into new fn xml_add_attr()

apps/restconf/restconf_main_native.c

@@ -634,7 +634,7 @@ restconf_clixon_backend(clicon_handle h,
 
     /* Loop to wait for backend starting, try again if not done */
     while (1){
-        if (clicon_hello_req(h, &id) < 0){
+        if (clicon_hello_req(h, "cl:restconf", NULL, &id) < 0){
             if (errno == ENOENT){
                 fprintf(stderr, "waiting");
                 sleep(1);