Update isVolumePathMounted log message

[songjiaxun]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind api-change
/kind bug
/kind cleanup
/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake

/kind cleanup

What this PR does / why we need it:

Clean up the logging message in isVolumePathMounted func that is used by both NodePublishVolume and NodeStageVolume functions.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[tyuchn]

/lgtm
/approve
/retest

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: songjiaxun, tyuchn

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