[VNET] VLAN sub interface RIFs are not assigned to VNET

[veber-alex]

Description

VLAN sub interfaces are not attached to VNET and appear in the global routing table.

Steps to reproduce the issue:

1. Load the following two configurations:

{
        "VXLAN_TUNNEL": {
                "tunnel_v4": {
                        "src_ip": "10.1.0.2" 
                }
        },
        "VNET": {
                "Vnet210": {
                        "vxlan_tunnel": "tunnel_v4",
                        "vni": "210",
                        "peer_list": "" 
                },
                "Vnet215": {
                        "vxlan_tunnel": "tunnel_v4",
                        "vni": "215",
                        "peer_list": "" 
                },
               "Vnet800": {
                        "vxlan_tunnel": "tunnel_v4",
                        "vni": "800",
                        "peer_list": "" 
                },
               "Vnet900": {
                        "vxlan_tunnel": "tunnel_v4",
                        "vni": "900",
                        "peer_list": "" 
                }
        },
        "VLAN_SUB_INTERFACE": {
                     "Ethernet124.210": {
                       "vnet_name": "Vnet210" 
                },
                     "Ethernet124.215": {
                       "vnet_name": "Vnet215" 
                }
        }
}

{
        "VLAN_SUB_INTERFACE": {
                "Ethernet124.210|172.2.10.254/24": {},
                "Ethernet124.215|172.2.15.254/24": {}
        }
}

Describe the results you received:

The RIFs are not attached to VNET and show in global routing table:

root@ptr-orion-t2:~/vnet/vnet_sub_eth# show ip int
Interface        Master    IPv4 address/mask    Admin/Oper    BGP Neighbor    Neighbor IP
---------------  --------  -------------------  ------------  --------------  -------------
Ethernet124.210            172.2.10.254/24      up/up         N/A             N/A
Ethernet124.215            172.2.15.254/24      up/up         N/A             N/A

root@ptr-orion-t2:~/vnet/vnet_sub_eth# show ip r
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR, f - OpenFabric,
       > - selected route, * - FIB route, q - queued route, r - rejected route

K>* 0.0.0.0/0 [0/202] via 10.130.0.1, eth0, 00:14:38
C>* 10.1.0.2/32 is directly connected, Loopback0, 00:14:38
B>* 10.1.0.3/32 [20/0] via 10.100.0.17, PortChannel1, 00:13:11
  *                    via 10.100.0.19, PortChannel2, 00:13:11
  *                    via 10.100.0.21, PortChannel3, 00:13:11
  *                    via 10.100.0.23, PortChannel4, 00:13:11
B>* 10.1.1.1/32 [20/0] via 10.100.0.17, PortChannel1, 00:13:11
  *                    via 10.100.0.19, PortChannel2, 00:13:11
  *                    via 10.100.0.21, PortChannel3, 00:13:11
  *                    via 10.100.0.23, PortChannel4, 00:13:11
C>* 10.100.0.16/31 is directly connected, PortChannel1, 00:13:28
C>* 10.100.0.18/31 is directly connected, PortChannel2, 00:13:27
C>* 10.100.0.20/31 is directly connected, PortChannel3, 00:13:27
C>* 10.100.0.22/31 is directly connected, PortChannel4, 00:13:27
C>* 10.130.0.0/16 is directly connected, eth0, 00:14:38
C>* 12.144.0.0/16 is directly connected, Vlan200, 00:13:28
B>* 14.144.0.0/16 [20/0] via 10.100.0.17, PortChannel1, 00:13:11
  *                      via 10.100.0.19, PortChannel2, 00:13:11
  *                      via 10.100.0.21, PortChannel3, 00:13:11
  *                      via 10.100.0.23, PortChannel4, 00:13:11
C>* 172.2.10.0/24 is directly connected, Ethernet124.210, 00:10:49
C>* 172.2.15.0/24 is directly connected, Ethernet124.215, 00:10:49

Describe the results you expected:
VLAN interface RIF should work with VNET the same way other RIF types.

Additional information you deem important (e.g. issue happens only occasionally):

**Output of `show version`:**

SONiC Software Version: SONiC.201911.0-c15674ee
Distribution: Debian 9.12
Kernel: 4.9.0-9-2-amd64
Build commit: c15674ee
Build date: Mon Feb 17 09:31:47 UTC 2020
Built by: stepanb@r-build-sonic03

Platform: x86_64-mlnx_msn2700-r0
HwSKU: Mellanox-SN2700-D48C8
ASIC: mellanox
Serial Number: MT1811X06319
Uptime: 09:12:37 up 6 days, 20:06,  2 users,  load average: 3.14, 3.26, 3.54

[liat-grozovik]

@rlhui and @lguohan any plan to handle this for 201911?