[PFCWD + Asym PFC]: PFC storm is not detected on lossy priorities when Asym PFC is enabled

[volodymyrsamotiy]

Observed behavior
PFCWD doesn't detect PFC storm on the lossy priorities for the port on which asymmetric PFC is enabled.

Expected behavior
According to requirements PFCWD should detect PFC storm on the lossy priorities for the port on which asymmetric PFC is enabled.
(when asymmetric PFC is enabled on some port that means such port is enabled for receiving PFC frames on all priorities)

Steps to reproduce

1. Enable asymmetric PFC on test port.

pfc config asymmetric on <port>

2. Enable PFCWD on the test port.

pfcwd start --action drop --restoration-time 3000 <port> 1000
pfcwd interval 500

3. Run pause frames to the test port for all priorities.
4. Verify that PFCWD detected storm only for lossless priorities.

pfcwd show stats

[qiluo-msft]

Happens on both master and 201811 branches