[PFCWD] Fix 'start' pfcwd command (sonic-net#1345)

- What I did
The 'config' method is getting arguments from the user CLI and build a proper command for the pfcwd script in a wrong way, causing this issue.

- How I did it
Fix the command structure to align with pfcwd.main script.

- How to verify it
Run "config pfcwd start --action drop ports all detection-time 400 --restoration-time 400"

- Previous command output (if the output of a command-line utility has changed)
config pfcwd start --action drop ports all detection-time 400 --restoration-time 400
Failed to run command, invalid options:
ports
detection-time

Author: shlomibitton

config/main.py

@@ -1685,10 +1685,10 @@ def start(action, restoration_time, ports, detection_time, verbose):
 
     if ports:
         ports = set(ports) - set(['ports', 'detection-time'])
-        cmd += " ports {}".format(' '.join(ports))
+        cmd += " {}".format(' '.join(ports))
 
     if detection_time:
-        cmd += " detection-time {}".format(detection_time)
+        cmd += " {}".format(detection_time)
 
     if restoration_time:
         cmd += " --restoration-time {}".format(restoration_time)