Fix expected neighbor output when multiple ports connect to same neig…

[lguohan]

…hbor

Previous code only enumerate on distinct neighbors, thus only one
port is shown for a neighbor.

Fix sonic-net/sonic-buildimage#5526

Signed-off-by: Guohan Lu [email protected]

- What I did
Previous code only enumerate on distinct neighbors, thus only one
port is shown for a neighbor.

- How I did it

• Fix expected neighbor output when multiple ports connect to same neighbor
• Add unit test
• Add fixture to select t1 topology database
• Introduce config/state/appl/asic/counter db for t1 topology

- How to verify it
Unit test and real dut

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

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

[lguohan]

retest this please

[lguohan]

test failure is due to a different issue