target-lun 0 can be delete when detaching volume.

[jangseon ryu]

target-lun 0 can delete when detaching volume.

Environment
===========
- OpenStack Release : Liberty
- OS : Ubuntu 14.04.2 LTS
- Hypervisor : KVM
- Cinder Storage : iSCSI (EMC VNX)

Description
===========
I am using EMC Storage as volume backend.
Recently, I discovered problem logic when detaching volume.
As you know, nova-compute try to delete device and mapper of detaching volume.

AFAIK, EMC Storage has lun-0 device in compute node.

$ls -al /dev/disk/by-path/*lun-0
lrwxrwxrwx 1 root root 9 Feb 24 20:05 ip-x.x.x.x:3260-iscsi-iqn.1992-04.com.emc:cx.ckm00142100690.a0-lun-0 -> ../../sdd
lrwxrwxrwx 1 root root 9 Feb 24 20:05 ip-x.x.x.x:3260-iscsi-iqn.1992-04.com.emc:cx.ckm00142100690.b0-lun-0 -> ../../sde
lrwxrwxrwx 1 root root 9 Feb 24 20:05 ip-x.x.x.x:3260-iscsi-iqn.1992-04.com.emc:cx.ckm00142100690.a1-lun-0 -> ../../sdi
lrwxrwxrwx 1 root root 9 Feb 24 20:05 ip-x.x.x.x:3260-iscsi-iqn.1992-04.com.emc:cx.ckm00142100690.b1-lun-0 -> ../../sdh

But nova-compute can delete device of lun-0 when failing to get 'target_lun'

https://github.com/openstack/nova/blob/stable/kilo/nova/virt/libvirt/volume.py
    def _delete_mpath(self, iscsi_properties, multipath_device, ips_iqns):
        entries = self._get_iscsi_devices()
        # Loop through ips_iqns to construct all paths
        iqn_luns = []
        for ip, iqn in ips_iqns:
            iqn_lun = '%s-lun-%s' %
                (iqn,iscsi_properties.get('target_lun', 0)) <-- return 0 (lun-id) when getting value of 'target_lun'

i think that it needs to modify that code.

[Takashi Natsume (natsume-takashi)]

Liberty is already EOL and this bug report has been 'In Progress' status for a year, but there is no activity. So set it to 'Invalid' status.
This bug can be reopened (set back to "New") if someone reproduce the bug at newton, ocata or master.