bridge: add json support for bridge vlan show

bridge: add json support for bridge vlan show

$bridge -c vlan show
port	vlan ids
swp1	 1 PVID Egress Untagged
	 10-13

swp2	 1 PVID Egress Untagged
	 10-13

br0	 1 PVID Egress Untagged

$bridge  -json vlan show
{
    "swp1": [{
            "vlan": 1,
            "flags": ["PVID","Egress Untagged"
            ]
        },{
            "vlan": 10
        },{
            "vlan": 11
        },{
            "vlan": 12
        },{
            "vlan": 13
        }
    ],
    "swp2": [{
            "vlan": 1,
            "flags": ["PVID","Egress Untagged"
            ]
        },{
            "vlan": 10
        },{
            "vlan": 11
        },{
            "vlan": 12
        },{
            "vlan": 13
        }
    ],
    "br0": [{
            "vlan": 1,
            "flags": ["PVID","Egress Untagged"
            ]
        }
    ]
}

$bridge -c -json vlan show
{
    "swp1": [{
            "vlan": 1,
            "flags": ["PVID","Egress Untagged"
            ]
        },{
            "vlan": 10,
            "vlanEnd": 13
        }
    ],
    "swp2": [{
            "vlan": 1,
            "flags": ["PVID","Egress Untagged"
            ]
        },{
            "vlan": 10,
            "vlanEnd": 13
        }
    ],
    "br0": [{
            "vlan": 1,
            "flags": ["PVID","Egress Untagged"
            ]
        }
    ]
}

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>