refactor: defer branch protection check (#1173)

lib/platform/github/index.js

lib/platform/gitlab/index.js

lib/platform/vsts/index.js

lib/workers/branch/parent.js

test/platform/__snapshots__/index.spec.js.snap

test/platform/github/__snapshots__/index.spec.js.snap

test/platform/github/index.spec.js

test/platform/gitlab/index.spec.js

test/platform/vsts/index.spec.js

test/workers/branch/parent.spec.js