drainErrChan returns if channel is closed (#4314) (#4315)

(cherry picked from commit 00550ca)

Co-authored-by: Anderson Queiroz <anderson.queiroz@elastic.co>

pkg/component/runtime/manager_test.go

@@ -3496,7 +3496,11 @@ func newDebugLogger(t *testing.T) *logger.Logger {
 func drainErrChan(ch chan error) {
 	for {
 		select {
-		case <-ch:
+		case _, ok := <-ch:
+			// channel is closed, nothing to drain
+			if !ok {
+				return
+			}
 		default:
 			return
 		}