Add "show queue-monitor length" command.

[denysaleksandrov]

Add parsing of json output of the command
"show queue-monitor length [interface] [limit] [seconds|sample] [seconds|samples]".

If merged on the Sand platforms will be possible to do this:

	showqueue := &module.ShowQueueMonitor{}
	showqueue.SetCmd("Et24/1", true, "seconds", 10)
	fmt.Println(showqueue.Cmd)

	handle, _ := node.GetHandle("json")
	if err = handle.Enable(showqueue); err != nil {
		panic(err)
	}

	fmt.Println(showqueue.ReportTime)
	fmt.Println(showqueue.GlobalHitCount)
	for _, entry := range showqueue.EntryList {
		fmt.Println(entry.Interface)
		fmt.Println(entry.EntryTime)
		fmt.Println(entry.EntryTimeUsecs)
		fmt.Println(entry.QueueLength)
		for _, port := range entry.IngressPortSet {
			fmt.Println(port)
		}
	}

go run arista_command.go                                                                                                                                                           40232❮ ◀12:16:39
show queue-monitor length Et24/1 limit 10 seconds
1.569233803510707e+09
0
Ethernet24/1
1.569233799625076e+09
1569233799625076
144336
Ethernet24/3
Ethernet13/1
Ethernet35/1
Ethernet23/1
Ethernet33/1
Ethernet19/1
Ethernet14/1
Ethernet18/1
Ethernet24/1
Ethernet34/1
Ethernet24/4
Ethernet24/2

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@49dadde). Click here to learn what that means.
The diff coverage is 72.72%.

@@            Coverage Diff            @@
##             master      #30   +/-   ##
=========================================
  Coverage          ?   88.81%           
=========================================
  Files             ?       21           
  Lines             ?     2190           
  Branches          ?        0           
=========================================
  Hits              ?     1945           
  Misses            ?      197           
  Partials          ?       48

Impacted Files	Coverage Δ
module/queue.go	72.72% <72.72%> (ø)

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[cheynearista]

The only request I would make relates to the method name. It may be better to rename this ShowQueueMonitorWithLimit() and remove the requirement for limit bool. You could then have another method ShowQueueMonitor() that performs the underlying call to SetCmd() with no limit set.

[denysaleksandrov]

Applied. There are two methods now as requested:
ShowQueueMonitorWithLimit()
ShowQueueMonitor()

show := module.Show(node)
showqueue, _ := show.ShowQueueMonitor("Et24/1")

or
show := module.Show(node)
showqueue, _ := show.ShowQueueMonitorWithLimit("Et24/1", "seconds", 60)

or
showqueueLimit := &module.ShowQueueMonitor{}
showqueueLimit.SetCmd("Et24/1", "seconds", 10)
showqueueNoLimit := &module.ShowQueueMonitor{}
showqueueNoLimit.SetCmd("Et24/1", "", 0)