Migrate /diagnostics and /service_nodes to be deployment agnostic#199645

miloszmarcinkowski merged 16 commits intoelastic:mainelastic/kibana:mainfrom

miloszmarcinkowski:198967-apm-migrate-testapm_api_integrationtestsdiagnostics-to-be-deployment-agnostic-api-testsmiloszmarcinkowski/kibana:198967-apm-migrate-testapm_api_integrationtestsdiagnostics-to-be-deployment-agnostic-api-testsCopy head branch name to clipboard