ipCidrRouteTable snmp walk fails

[tbgowda]

Description

SNMP walk for OID 1.3.6.1.2.1.4.24.4 fails to provide any info

Steps to reproduce the issue:

1. Bring up Sonic VS T1 topology
2. Make sure BGP neighborship is established and routes are populated
3. Trigger SNMP walk : snmpwalk -v 2c -c public 1.3.6.1.2.1.4.24.4

Describe the results you received:
vxr@ubuntu:~$ snmpwalk -v 2c -c public 10.250.0.105 1.3.6.1.2.1.4.24.4
iso.3.6.1.2.1.4.24.4 = No Such Object available on this agent at this OID

Describe the results you expected:

IP routing entries

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

Looking at rfc4292.py:RouteUpdater:update_data, it seems like we skip all IP addresses that are not 0.0.0.0/0. Is that intentional?

**Output of `show version`:**

root@vlab-03:/home/admin# show ver

SONiC Software Version: SONiC.master.565-e0781f46
Distribution: Debian 10.6
Kernel: 4.19.0-9-2-amd64
Build commit: e0781f4
Build date: Mon Nov 23 08:32:04 UTC 2020
Built by: johnar@jenkins-worker-12

Platform: x86_64-kvm_x86_64-r0
HwSKU: Force10-S6000
ASIC: vs
Serial Number: 000000
Uptime: 02:40:04 up 1:41, 1 user, load average: 1.07, 0.65, 0.70

Docker images:
REPOSITORY TAG IMAGE ID SIZE
docker-gbsyncd-vs latest fc2bcaf7dc91 447MB
docker-gbsyncd-vs master.565-e0781f46 fc2bcaf7dc91 447MB
docker-syncd-vs latest a599f4b6a7c9 447MB
docker-syncd-vs master.565-e0781f46 a599f4b6a7c9 447MB
docker-snmp latest 72953533ec0e 477MB
docker-snmp master.565-e0781f46 72953533ec0e 477MB
docker-teamd latest 0392627a102f 483MB
docker-teamd master.565-e0781f46 0392627a102f 483MB
docker-nat latest 61210a29630f 486MB
docker-nat master.565-e0781f46 61210a29630f 486MB
docker-router-advertiser latest dcc0e15c5463 441MB
docker-router-advertiser master.565-e0781f46 dcc0e15c5463 441MB
docker-platform-monitor latest 053ce63c0b8f 563MB
docker-platform-monitor master.565-e0781f46 053ce63c0b8f 563MB
docker-lldp latest c68597acb666 514MB
docker-lldp master.565-e0781f46 c68597acb666 514MB
docker-dhcp-relay latest badb3fb27c4e 448MB
docker-dhcp-relay master.565-e0781f46 badb3fb27c4e 448MB
docker-database latest d92f5b4cb6e0 441MB
docker-database master.565-e0781f46 d92f5b4cb6e0 441MB
docker-orchagent latest d9c215c333d9 497MB
docker-orchagent master.565-e0781f46 d9c215c333d9 497MB
docker-sonic-telemetry latest 26941527084a 511MB
docker-sonic-telemetry master.565-e0781f46 26941527084a 511MB
docker-sonic-mgmt-framework latest d92d56dac3a5 598MB
docker-sonic-mgmt-framework master.565-e0781f46 d92d56dac3a5 598MB
docker-fpm-frr latest 6c139d86ef63 500MB
docker-fpm-frr master.565-e0781f46 6c139d86ef63 500MB
docker-sflow latest 883128578286 484MB
docker-sflow master.565-e0781f46 883128578286 484MB

**Attach debug file `sudo generate_dump`:**

```
(paste your output here)
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