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()

lib/src/clixon_xml_map.c

@@ -648,7 +648,6 @@ xml_namespace_change(cxobj *x,
        /* Add prefix to x, if any */
        if (prefix && xml_prefix_set(x, prefix) < 0)
            goto done;
-       
     }
  ok:
     retval = 0;