Since the commit below mdb's json output has been invalid and also with
changed format. Restore it to a valid json like the previous format.
Also takes care of a double "Deleted" print when monitoring for changes.

Example bridge -p -d -j mdb show:
 [ {
        "mdb": [ {
                "index": 4,
                "dev": "virbr0",
                "port": "vnet2",
                "grp": "ff02::202",
                "state": "temp",
                "flags": [ ]
            },{
                "index": 4,
                "dev": "virbr0",
                "port": "vnet2",
                "grp": "ff02::1:fffb:1939",
                "state": "temp",
                "flags": [ ]
            },{
                "index": 6,
                "dev": "virbr1",
                "port": "vnet7",
                "grp": "ff02::202",
                "state": "temp",
                "flags": [ ]
            },{
                "index": 6,
                "dev": "virbr1",
                "port": "vnet7",
                "grp": "ff02::1:ffd0:f61f",
                "state": "temp",
                "flags": [ ]
            } ],
        "router": {
            "virbr0": [ {
                    "port": "vnet1"
                },{
                    "port": "vnet0"
                } ],
            "virbr1": [ {
                    "port": "vnet5"
                } ]
        }
    } ]

Fixes: c7c1a1ef ("bridge: colorize output and use JSON print library")
Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>