Add port counter sanity check

[jimmyzhai]

What I did
Fix issue sonic-net/sonic-buildimage#10850 partially by adding sanity check in port_rates.lua. If the must-have counters of one port are not able to get, skip its rate computation.

Why I did it
It avoids port_rates.lua execution exits abnormally.

How I verified it

Capture and return error message if the needed counters of the port do not exist.

root@DUT:/# redis-cli --eval ./port_rates.lua oid:0x1000000000012 , 2 COUNTERS 10

1) "0.18"

2) "0.82"

3) "10"

4) "COUNTERS_LAST"

5) "Not found some counters on oid:0x1000000000012"

root@DUT:/# redis-cli --eval ./port_rates.lua oid:0x1000000000010  , 2 COUNTERS 10

1) "0.18"

2) "0.82"

3) "10"

4) "DONE"

Details if related

[lguohan]

can you add full description? how you did it? how is it verified?

[jimmyzhai]

can you add full description? how you did it? how is it verified?

Added