Fix panic: concurrent write to websocket

[fisherxu]

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 test
/kind failing-test
/kind feature

What this PR does / why we need it:
routeToCloud and keeplive are two goroutines, if there's no lock here, edgecore will panic when they concurrent write to websocket connection.
Which issue(s) this PR fixes:

Fixes #1017

Special notes for your reviewer:
/cc @kevin-wangzefeng @kadisi @alien19880726
Does this PR introduce a user-facing change?:

NONE

[kubeedge-bot]

@fisherxu: GitHub didn't allow me to request PR reviews from the following users: alien19880726.

Note that only kubeedge members and repo collaborators can review this PR, and authors cannot review their own PRs.

In response to this:

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 test
/kind failing-test
/kind feature

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #1017

Special notes for your reviewer:
/cc @kevin-wangzefeng @kadisi @alien19880726
Does this PR introduce a user-facing change?:

NONE

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[fisherxu]

/cc @alien19880726

[kubeedge-bot]

@fisherxu: GitHub didn't allow me to request PR reviews from the following users: alien19880726.

Note that only kubeedge members and repo collaborators can review this PR, and authors cannot review their own PRs.

In response to this:

/cc @alien19880726

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[kevin-wangzefeng]

/approve

[kubeedge-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kevin-wangzefeng

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• OWNERS [kevin-wangzefeng]

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[kadisi]

/lgtm