resources: aws: ec2: Fix closed channel handling

If awschan closes, longpollWatch and snsWatch return nil
instead of an error. This will prevent the engine from
shutting down in case we choose to close the channel
early or from other struct methods.

resources/aws_ec2.go

@@ -469,7 +469,7 @@ func (obj *AwsEc2Res) longpollWatch() error {
 			}
 		case msg, ok := <-obj.awsChan:
 			if !ok {
-				return fmt.Errorf("channel closed unexpectedly")
+				return nil
 			}
 			if err := msg.err; err != nil {
 				return err
@@ -650,7 +650,7 @@ func (obj *AwsEc2Res) snsWatch() error {
 			}
 		case msg, ok := <-obj.awsChan:
 			if !ok {
-				return *exit
+				return nil
 			}
 			if err := msg.err; err != nil {
 				return err