AWS volumes: Release disk from attaching map on error

If AWS gives us an actual error (vs just timing out), we know the disk
did not attach, and so we can remove it immediately from the attaching
map.

pkg/cloudprovider/providers/aws/aws.go

@@ -1144,6 +1144,8 @@ func (self *awsDisk) describeVolume() (*ec2.Volume, error) {
 	return volumes[0], nil
 }
 
+// waitForAttachmentStatus polls until the attachment status is the expected value
+// TODO(justinsb): return (bool, error)
 func (self *awsDisk) waitForAttachmentStatus(status string) error {
 	// TODO: There may be a faster way to get this when we're attaching locally
 	attempt := 0
@@ -1278,9 +1280,11 @@ func (c *AWSCloud) AttachDisk(diskName string, instanceName string, readOnly boo
 		ec2Device = "/dev/sd" + string(mountDevice)
 	}
 
-	attached := false
+	// attachEnded is set to true if the attach operation completed
+	// (successfully or not)
+	attachEnded := false
 	defer func() {
-		if attached {
+		if attachEnded {
 			awsInstance.endAttaching(disk.awsID, mountDevice)
 		}
 	}()
@@ -1294,6 +1298,7 @@ func (c *AWSCloud) AttachDisk(diskName string, instanceName string, readOnly boo
 
 		attachResponse, err := c.ec2.AttachVolume(request)
 		if err != nil {
+			attachEnded = true
 			// TODO: Check if the volume was concurrently attached?
 			return "", fmt.Errorf("Error attaching EBS volume: %v", err)
 		}
@@ -1306,7 +1311,7 @@ func (c *AWSCloud) AttachDisk(diskName string, instanceName string, readOnly boo
 		return "", err
 	}
 
-	attached = true
+	attachEnded = true
 
 	return hostDevice, nil
 }