fix error: interface counters is mismatch after warm-reboot (#5346)

- Why I did it
There is a issue for counters after warm-reboot:
If I clear counters by command "sonic-clear counters", then execute 'warm-reboot' and whenSONiC is restart, the counters showed with command "show interface counters" is still old counters before "sonic-clear". It is not the right counters because the counters file in '/tmp' is lost in warm-reboot process.

- How I did it
I fixed it by saving '/tmp/portstat-0' folders in '/host/' before executing 'warm-reboot' (in pull request Azure/sonic-utilities#1099 ), and restore the counters folders back to '/tmp/' after warm-reboot process is finished.

- How to verify it

Clear counters by command 'sonic-clear'
sonic-clear counters
sonic-clear dropcounters
sonic-clear pfccounters
sonic-clear queuecounters
sonic-clear rifcounters
Execute 'warm-reboot'
Use command ‘show interface counters’ to see if the counters is right.

files/image_config/warmboot-finalizer/finalize-warmboot.sh

@@ -76,6 +76,20 @@ function stop_control_plane_assistant()
     fi
 }
 
+function restore_counters_folder()
+{
+    debug "Restoring counters folder after warmboot..."
+
+    modules=("portstat-0" "dropstat" "pfcstat-0" "queuestat-0" "intfstat-0")
+    for module in ${modules[@]}
+    do
+        statfile="/host/counters/$module"
+        if [[ -d $statfile ]]; then
+            mv $statfile /tmp/
+        fi
+    done
+}
+
 
 wait_for_database_service
 
@@ -86,6 +100,8 @@ if [[ x"${WARM_BOOT}" != x"true" ]]; then
     exit 0
 fi
 
+restore_counters_folder
+
 list=${COMP_LIST}
 
 # Wait up to 5 minutes