tests/e2e: investigating TestCtlV3AuthAndWatch failure in coverage tests

[gyuho]

=== RUN   TestCtlV3AuthAndWatch
--- FAIL: TestCtlV3AuthAndWatch (2.11s)
	ctl_v3_auth_test.go:856: watchTest #0: ctlV3Watch error (read /dev/ptmx: input/output error)
	ctl_v3_auth_test.go:856: watchTest #1: ctlV3Watch error (read /dev/ptmx: input/output error)
	ctl_v3_auth_test.go:856: watchTest #2: ctlV3Watch error (read /dev/ptmx: input/output error)
	ctl_v3_auth_test.go:856: watchTest #3: ctlV3Watch error (read /dev/ptmx: input/output error)

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@62dfb89). Click here to learn what that means.
The diff coverage is 0%.

@@            Coverage Diff            @@
##             master    #9684   +/-   ##
=========================================
  Coverage          ?   68.73%           
=========================================
  Files             ?      373           
  Lines             ?    34762           
  Branches          ?        0           
=========================================
  Hits              ?    23893           
  Misses            ?     9136           
  Partials          ?     1733

Impacted Files	Coverage Δ
etcdctl/ctlv3/command/watch_command.go	45.91% <0%> (ø)

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[hexfusion]

ref: #9419