print error log when remote proxy is trapped into errorHandler

[Congrool]

What type of PR is this?

/kind bug

What this PR does / why we need it:

We should treat the log of reverseProxy.ErrorHandler as error log. It will help us to find the problem of yurthub, such as x509 error during bootstrap.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

other Note

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In response to this:

What type of PR is this?

/kind bug

What this PR does / why we need it:

We should treate the log of reverseProxy.ErrorHandler as error log. It will help us to find the problem of yurthub, such as x509 error during bootstrap.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

other Note

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[rambohe-ch]

/lgtm
/approve

[openyurt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Congrool, rambohe-ch

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