Upgrade fsnotify to 1.6, make code more readable.

[yanggangtony]

/kind cleanup

What this PR does / why we need it:

As fsnotify 1.6.0 releasesd.

if event.Op&Write == Write && !(event.Op&Remove == Remove) {
  }
Becomes:

  if event.Has(Write) && !event.Has(Remove) {
  }

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[RainbowMango]

/assign @XiShanYongYe-Chang

[XiShanYongYe-Chang]

Hi @yanggangtony, I'm sorry, I totally missed this pr.