mtping now uses bucket-based leader election

[lionelvillard]

Depends on #4008
Depends on knative/pkg#1683

Proposed Changes

• 🎁 the mt adapter main now uses bucket-based leader election
• 🗑️ remove eventing leader election fork

Release Note

Docs

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lionelvillard

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• OWNERS [lionelvillard]

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[knative-test-reporter-robot]

The following jobs failed:

Test name	Triggers	Retries
pull-knative-eventing-conformance-tests	2020-09-05 22:53:44 +0000 UTC	1/3

Automatically retrying due to test flakiness...
/test pull-knative-eventing-conformance-tests

[knative-test-reporter-robot]

The following jobs failed:

Test name	Triggers	Retries
pull-knative-eventing-integration-tests	2020-09-05 22:53:45.004 +0000 UTC	1/3

Automatically retrying due to test flakiness...
/test pull-knative-eventing-integration-tests

[knative-metrics-robot]

The following is the coverage report on the affected files.
Say /test pull-knative-eventing-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/adapter/mtping/adapter.go	79.5%	77.8%	-1.7
pkg/adapter/v2/config.go	60.0%	55.6%	-4.4
pkg/adapter/v2/context.go	Do not exist	100.0%
pkg/adapter/v2/main.go	61.1%	51.1%	-9.9
pkg/adapter/v2/main_message.go	55.6%	52.6%	-2.9

[cr22rc]

/lgtm

[lionelvillard]

/test pull-knative-eventing-unit-tests