Vnet_route_check TCP socket for DB connection.

[siqbal1986]

Currently the Vnet_route_check fails if a user calls it witout sudo with the following error.

Traceback (most recent call last):
  File "/usr/local/bin/vnet_route_check.py", line 401, in <module>
    sys.exit(main())
  File "/usr/local/bin/vnet_route_check.py", line 364, in main
    if not check_vnet_cfg():
  File "/usr/local/bin/vnet_route_check.py", line 77, in check_vnet_cfg
    db = swsscommon.DBConnector('APPL_DB', 0)
  File "/usr/lib/python3/dist-packages/swsscommon/swsscommon.py", line 1656, in __init__
    _swsscommon.DBConnector_swiginit(self, _swsscommon.new_DBConnector(*args))
RuntimeError: Unable to connect to redis (unix-socket): Cannot assign requested address

What I did

The route_check script accesses the same DB tables but is able to run without the sudo rights. To solve this problem I have changed the Vnet_route_check to use a TCP socket to connect to the DB as done in route_check. As a result the script doesn't fail with a run time error.

How I did it

How to verify it

create a new user on a T1 device which has no docker or sudoers privilage. run vnet_route check. it should fail.

Previous command output (if the output of a command-line utility has changed)

Traceback (most recent call last):
  File "/usr/local/bin/vnet_route_check.py", line 401, in <module>
    sys.exit(main())
  File "/usr/local/bin/vnet_route_check.py", line 364, in main
    if not check_vnet_cfg():
  File "/usr/local/bin/vnet_route_check.py", line 77, in check_vnet_cfg
    db = swsscommon.DBConnector('APPL_DB', 0)
  File "/usr/lib/python3/dist-packages/swsscommon/swsscommon.py", line 1656, in __init__
    _swsscommon.DBConnector_swiginit(self, _swsscommon.new_DBConnector(*args))
RuntimeError: Unable to connect to redis (unix-socket): Cannot assign requested address

New command output (if the output of a command-line utility has changed)

None

[prsunny]

@qiluo-msft , can you merge this?