Fix slash in path.

[xincunli-sonic]

What I did

Addressing issue #3444. The issue caused by unescape in JsonPointer implementation which followed RFC 6901

pointer = jsonpointer.JsonPointer(path)

...

class JsonPointer(object):
    """A JSON Pointer that can reference parts of a JSON document"""

    # Array indices must not contain:
    # leading zeros, signs, spaces, decimals, etc
    _RE_ARRAY_INDEX = re.compile('0|[1-9][0-9]*$')
    _RE_INVALID_ESCAPE = re.compile('(~[^01]|~$)')

    def __init__(self, pointer):

        # validate escapes
        invalid_escape = self._RE_INVALID_ESCAPE.search(pointer)
        if invalid_escape:
            raise JsonPointerException('Found invalid escape {}'.format(
                invalid_escape.group()))

        parts = pointer.split('/')
        if parts.pop(0) != '':
            raise JsonPointerException('Location must start with /')

        parts = [unescape(part) for part in parts]
        self.parts = parts

How I did it

Re-escape / to ~1 to match the real key in json, and JsonPatch will handle it correctly.

How to verify it

admin@str2-7250-lc1-2:~$ cat link.json 
[
    {
        "op": "add",
        "path": "/asic1/PORTCHANNEL_INTERFACE/PortChannel106|10.0.0.6~131",
        "value": {}
    }
]
admin@str2-7250-lc1-2:~$ sudo config apply-patch link.json 
sonic_yang(6):Note: Below table(s) have no YANG models: DHCP_SERVER
sonic_yang(6):Note: Below table(s) have no YANG models: LOGGER
sonic_yang(6):Note: Below table(s) have no YANG models: LOGGER
Patch Applier: asic1: Patch application starting.
Patch Applier: asic1: Patch: [{"op": "add", "path": "/PORTCHANNEL_INTERFACE/PortChannel106|10.0.0.6~131", "value": {}}]
Patch Applier: asic1 getting current config db.
Patch Applier: asic1: simulating the target full config after applying the patch.
Patch Applier: asic1: validating all JsonPatch operations are permitted on the specified fields
Patch Applier: asic1: validating target config does not have empty tables,
                            since they do not show up in ConfigDb.
Patch Applier: asic1: sorting patch updates.
Patch Applier: The asic1 patch was converted into 0 changes.
Patch Applier: asic1: applying 0 changes in order.
Patch Applier: asic1: verifying patch updates are reflected on ConfigDB.
Patch Applier: asic1 patch application completed.
Patch applied successfully.

Previous command output (if the output of a command-line utility has changed)

New command output (if the output of a command-line utility has changed)