…tion" field of PORT_TABLE entries in APPL_DB or CONFIG_DB. (sonic-net#224)

- What I did
This is a correction of sonic-net#218, which is contained in sonic-net/sonic-buildimage#7859, after community decided that entries under .1.3.6.1.2.1.31.1.1.1.18 OID should return the "description" field of PORT_TABLE entries in APPL_DB or CONFIG_DB. For vlan, management and LAG, these are empty strings.
- How I did it
Deleted the lines of code quoted by Suvarna in the above PRs. This necessitated modifying 4 unit tests that had been written under the assumption that these OIDs would return non-empty data.
- How to verify it
Run unit tests in build and snmp tests in sonic-mgmt.
- Description for the changelog
Entries under .1.3.6.1.2.1.31.1.1.1.18 OID should return the "description" field of PORT_TABLE entries in APPL_DB or CONFIG_DB.

Signed-off-by: Raphael Tryster <raphaelt@nvidia.com>
(cherry picked from commit 0813b42)

…tion" field of PORT_TABLE entries in APPL_DB or CONFIG_DB. (sonic-net#224)

- What I did
This is a correction of sonic-net#218, which is contained in sonic-net/sonic-buildimage#7859, after community decided that entries under .1.3.6.1.2.1.31.1.1.1.18 OID should return the "description" field of PORT_TABLE entries in APPL_DB or CONFIG_DB. For vlan, management and LAG, these are empty strings.
- How I did it
Deleted the lines of code quoted by Suvarna in the above PRs. This necessitated modifying 4 unit tests that had been written under the assumption that these OIDs would return non-empty data.
- How to verify it
Run unit tests in build and snmp tests in sonic-mgmt.
- Description for the changelog
Entries under .1.3.6.1.2.1.31.1.1.1.18 OID should return the "description" field of PORT_TABLE entries in APPL_DB or CONFIG_DB.

Signed-off-by: Raphael Tryster <raphaelt@nvidia.com>
(cherry picked from commit 0813b42)

… for RFC2863 (#279)

**- What I did**
Cherry-pick the required PRs to 202012 Branch to add SNMP VLAN Support.
This is done because the VLAN if index comes in ipNetToMediaPhysAddress (1.3.6.1.2.1.4.22.1.2) but not in ifName 1.3.6.1.2.1.31.1.1.1.1.

**- How I did it**
Cherry-pick below PRs:
#218 - Main change
#224 - Follow up PR
#237 - Follow up PR

**- How to verify it**
Before PR changes:
```
admin@str2-sn3800-02:~$ docker exec -it snmp snmpwalk -v2c -c msft 127.0.0.1 1.3.6.1.2.1.31.1.1.1.1
iso.3.6.1.2.1.31.1.1.1.1.1 = STRING: "etp1a"
iso.3.6.1.2.1.31.1.1.1.1.3 = STRING: "etp1b"
iso.3.6.1.2.1.31.1.1.1.1.5 = STRING: "etp2a"
iso.3.6.1.2.1.31.1.1.1.1.7 = STRING: "etp2b"
iso.3.6.1.2.1.31.1.1.1.1.9 = STRING: "etp3a"
iso.3.6.1.2.1.31.1.1.1.1.11 = STRING: "etp3b"
..
iso.3.6.1.2.1.31.1.1.1.1.255 = STRING: "etp64b"
iso.3.6.1.2.1.31.1.1.1.1.1101 = STRING: "PortChannel101"
iso.3.6.1.2.1.31.1.1.1.1.1102 = STRING: "PortChannel102"
iso.3.6.1.2.1.31.1.1.1.1.1103 = STRING: "PortChannel103"
iso.3.6.1.2.1.31.1.1.1.1.1104 = STRING: "PortChannel104"
iso.3.6.1.2.1.31.1.1.1.1.10000 = STRING: "eth0"
```

After PR changes; Can see vlan 1000 with ifindex3000:
```
admin@str2-sn3800-02:~$ docker exec -it snmp snmpwalk -v2c -c msft 127.0.0.1 1.3.6.1.2.1.31.1.1.1.1
iso.3.6.1.2.1.31.1.1.1.1.1 = STRING: "etp1a"
iso.3.6.1.2.1.31.1.1.1.1.3 = STRING: "etp1b"
iso.3.6.1.2.1.31.1.1.1.1.5 = STRING: "etp2a"
iso.3.6.1.2.1.31.1.1.1.1.7 = STRING: "etp2b"
iso.3.6.1.2.1.31.1.1.1.1.9 = STRING: "etp3a"
iso.3.6.1.2.1.31.1.1.1.1.11 = STRING: "etp3b"
..
iso.3.6.1.2.1.31.1.1.1.1.255 = STRING: "etp64b"
iso.3.6.1.2.1.31.1.1.1.1.1101 = STRING: "PortChannel101"
iso.3.6.1.2.1.31.1.1.1.1.1102 = STRING: "PortChannel102"
iso.3.6.1.2.1.31.1.1.1.1.1103 = STRING: "PortChannel103"
iso.3.6.1.2.1.31.1.1.1.1.1104 = STRING: "PortChannel104"
iso.3.6.1.2.1.31.1.1.1.1.3000 = STRING: "Vlan1000"       
iso.3.6.1.2.1.31.1.1.1.1.10000 = STRING: "eth0"
```
UT Passes

…tion" field of PORT_TABLE entries in APPL_DB or CONFIG_DB. (sonic-net#224)

- What I did
This is a correction of sonic-net#218, which is contained in sonic-net/sonic-buildimage#7859, after community decided that entries under .1.3.6.1.2.1.31.1.1.1.18 OID should return the "description" field of PORT_TABLE entries in APPL_DB or CONFIG_DB. For vlan, management and LAG, these are empty strings.
- How I did it
Deleted the lines of code quoted by Suvarna in the above PRs. This necessitated modifying 4 unit tests that had been written under the assumption that these OIDs would return non-empty data.
- How to verify it
Run unit tests in build and snmp tests in sonic-mgmt.
- Description for the changelog
Entries under .1.3.6.1.2.1.31.1.1.1.18 OID should return the "description" field of PORT_TABLE entries in APPL_DB or CONFIG_DB.

Signed-off-by: Raphael Tryster <raphaelt@nvidia.com>