[watermark] Fix error: BUFFER_POOL_WATERMARK isn't enabled by default (sonic-net#4882)

* Fix error: watermarkstat -t buffer_pool doesn't work

Signed-off-by: Stephen Sun <[email protected]>

Author: stephenxs

dockers/docker-orchagent/enable_counters.py

@@ -17,6 +17,7 @@ def enable_counters():
     enable_counter_group(db, 'PFCWD')
     enable_counter_group(db, 'PG_WATERMARK')
     enable_counter_group(db, 'QUEUE_WATERMARK')
+    enable_counter_group(db, 'BUFFER_POOL_WATERMARK')
 
 def get_uptime():
     with open('/proc/uptime') as fp: