Refactored instrumented for more consistent API with runnable.

[bwplotka]

Signed-off-by: Bartlomiej Plotka bwplotka@gmail.com

[bwplotka]

This does not work as expected:

	for _, t := range instr.MetricTargets() {
			scfg.ServiceDiscoveryConfig.StaticConfigs[0].Targets = append(scfg.ServiceDiscoveryConfig.StaticConfigs[0].Targets, map[model.LabelName]model.LabelValue{
				model.AddressLabel:     model.LabelValue(t.InternalEndpoint),
				model.SchemeLabel:      model.LabelValue(strings.ToLower(t.Scheme)),
				model.MetricsPathLabel: model.LabelValue(t.MetricPath),
			})
		}
		cfg.ScrapeConfigs = append(cfg.ScrapeConfigs, scfg)

[bwplotka]

Works, rdy to be merged.