reduce log verbosity for metrics "receive stop signal"

[Links2004]

What type of PR is this?
/kind cleanup

What this PR does / why we need it:

reduce log verbosity for metrics "receive stop signal".

currently the log is cluttered with "receive stop signal, so stop metrics scan ..."
e.g.:

I0406 11:21:42.146160     797 edgedmetricsconnection.go:136] receive stop signal, so stop metrics scan ...
I0406 11:21:42.411512     797 edgedmetricsconnection.go:136] receive stop signal, so stop metrics scan ...
I0406 11:21:57.266068     797 edgedmetricsconnection.go:136] receive stop signal, so stop metrics scan ...
I0406 11:21:57.561080     797 edgedmetricsconnection.go:136] receive stop signal, so stop metrics scan ...
I0406 11:22:12.160770     797 edgedmetricsconnection.go:136] receive stop signal, so stop metrics scan ...
I0406 11:22:12.455189     797 edgedmetricsconnection.go:136] receive stop signal, so stop metrics scan ...

this kind of log entrys do not help during normal operation and are created for each request of the metrics-server as a result i decresed the verbosity of them to the same level that is used in the rest of the file.

Special notes for your reviewer:

Does this PR introduce a user-facing change?:
NONE

reduce log verbosity for metrics endpoint logs "receive stop signal".

[wbc6080]

/lgtm
Thanks for your contribution!

[Links2004]

/retest
how to trigger a rerun of the failed tests?

[kubeedge-bot]

@Links2004: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest
how to trigger a rerun of the failed tests?

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[Links2004]

@wbc6080 can you please restart the tests, so that this can be merged?

[wbc6080]

I took a look and found that we have fixed the failed ci test in other PRs. You can rebase the latest code to try again.

[kubeedge-bot]

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[Links2004]

please approve the run of the CI/CD

[wbc6080]

Could you help to run the CI test? thanks @WillardHu @Shelley-BaoYue @fisherxu