Pass X-Vcap-Request-Id header in calls to BBS

[mariash]

• A short explanation of the proposed change:

To support distributed tracing request id received from the Gorouter is passed to Diego BBS so that the same request can be traced along multiple components.

• An explanation of the use cases your change solves

This is part of distributed tracing feature - the ability to trace the same request across multiple components, e.g. stopping an app instance first will come to Gorouter, which will generate request ID and pass it down to Cloud Controller, which will pass it to Diego BBS, which will pass it to downstream components like Auctioneer, Rep and Garden.

• I have reviewed the contributing guide

• I have viewed, signed, and submitted the Contributor License Agreement

• I have made this pull request to the main branch

• I have run all the unit tests using bundle exec rake

• I have run CF Acceptance Tests

[sethboyles]

We were curious why there was an extra uuid appended to the original vcap request id, and it seems like it was carrying over behavior explained in this comment?

cloud_controller_ng/lib/sinatra/vcap.rb

Lines 103 to 110 in 0a410b1

	# we append a new guid to the request because we have no idea if the
	# caller is really going to be giving us a unique guid, i.e. they might
	# generate the guid and then turn around and make 3 api calls using it.
	if @request_guid
	@request_guid = "#{@request_guid}::#{SecureRandom.uuid}"
	else
	@request_guid ||= SecureRandom.uuid
	end