[backport][fix][websocket] Connection header must include not match Upgrade

[Rechi]

Description

RFC 6455 4.1. Client Requirements
The request MUST contain a |Connection| header field whose value MUST include the "Upgrade" token.

backports #13001

Motivation and Context

newer Firefox versions send Connection: keep-alive, Upgrade

How Has This Been Tested?

Tested with Firefox 56.

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the Code guidelines of this project
• My change requires a change to the documentation, either Doxygen or wiki
• I have updated the documentation accordingly
• I have read the CONTRIBUTING document
• I have added tests to cover my change
• All new and existing tests passed