T160: Rebase and fixes for NAT64

 - Update the base (rebase)
 - Move include/nat64-protocol.xml.i => include/nat64/protocol.xml.i
 - Delete unwanted `write_json`, use `write_file` instead
 - Remove unnecessary deleting of default values for tagNodes T2665
 - Add smoketest

Example:
```
set interfaces ethernet eth0 address '192.168.122.14/24'
set interfaces ethernet eth0 address '192.168.122.10/24'
set interfaces ethernet eth2 address '2001:db8::1/64'

set nat64 source rule 100 source prefix '64:ff9b::/96'
set nat64 source rule 100 translation pool 10 address '192.168.122.10'
set nat64 source rule 100 translation pool 10 port '1-65535'
```

1 files changed, 0 insertions, 14 deletions

diff --git a/python/vyos/utils/file.py b/python/vyos/utils/file.py
index 2b1f23b34..9f27a7fb9 100644
--- a/python/vyos/utils/file.py
+++ b/python/vyos/utils/file.py
@@ -83,20 +83,6 @@ def read_json(fname, defaultonfailure=None):
             return defaultonfailure
         raise e
 
-def write_json(fname, data, indent=2, defaultonfailure=None):
-    """
-    encode data to json and write to a file
-    should defaultonfailure be not None, it is returned on failure to write
-    """
-    import json
-    try:
-        with open(fname, 'w') as f:
-            json.dump(data, f, indent=indent)
-    except Exception as e:
-        if defaultonfailure is not None:
-            return defaultonfailure
-        raise e
-
 def chown(path, user, group):
     """ change file/directory owner """
     from pwd import getpwnam