Add tests for leadership election

Pull liveness into leadership to ease testing, logically the liveness
probe is directly affected by leadership so it makes sense here.

Moved some of the components of the controller tests into the testutil
package for reuse in my own tests.

internal/pkg/handler/create.go

@@ -19,6 +19,7 @@ func (r ResourceCreatedHandler) Handle() error {
 		logrus.Errorf("Resource creation handler received nil resource")
 	} else {
 		config, _ := r.GetConfig()
+		// process resource based on its type
 		return doRollingUpgrade(config, r.Collectors)
 	}
 	return nil

internal/pkg/handler/update.go

@@ -21,6 +21,7 @@ func (r ResourceUpdatedHandler) Handle() error {
 	} else {
 		config, oldSHAData := r.GetConfig()
 		if config.SHAValue != oldSHAData {
+			// process resource based on its type
 			return doRollingUpgrade(config, r.Collectors)
 		}
 	}