create snapshot failed

[TommyLike]

When creating snapshot, we could delete the volume right after the creation of snapshot record in database, that means the cinder-volume service could not really create snapshot at backend and the snapshot can never be deletable again.

ERROR log:
```
Dec 25 14:25:02 SZX1000299228 cinder-volume[30425]: ERROR oslo_messaging.rpc.server File "/opt/stack/cinder/cinder/objects/cleanable.py", line 207, in wrapper
Dec 25 14:25:02 SZX1000299228 cinder-volume[30425]: ERROR oslo_messaging.rpc.server result = f(*args, **kwargs)
Dec 25 14:25:02 SZX1000299228 cinder-volume[30425]: ERROR oslo_messaging.rpc.server File "/opt/stack/cinder/cinder/volume/manager.py", line 1067, in create_snapshot
Dec 25 14:25:02 SZX1000299228 cinder-volume[30425]: ERROR oslo_messaging.rpc.server snapshot.save()
Dec 25 14:25:02 SZX1000299228 cinder-volume[30425]: ERROR oslo_messaging.rpc.server File "/usr/local/lib/python2.7/dist-packages/oslo_utils/excutils.py", line 220, in __exit__
Dec 25 14:25:02 SZX1000299228 cinder-volume[30425]: ERROR oslo_messaging.rpc.server self.force_reraise()
Dec 25 14:25:02 SZX1000299228 cinder-volume[30425]: ERROR oslo_messaging.rpc.server File "/usr/local/lib/python2.7/dist-packages/oslo_utils/excutils.py", line 196, in force_reraise
Dec 25 14:25:02 SZX1000299228 cinder-volume[30425]: ERROR oslo_messaging.rpc.server six.reraise(self.type_, self.value, self.tb)
Dec 25 14:25:02 SZX1000299228 cinder-volume[30425]: ERROR oslo_messaging.rpc.server File "/opt/stack/cinder/cinder/volume/manager.py", line 1059, in create_snapshot
Dec 25 14:25:02 SZX1000299228 cinder-volume[30425]: ERROR oslo_messaging.rpc.server model_update = self.driver.create_snapshot(snapshot)
Dec 25 14:25:02 SZX1000299228 cinder-volume[30425]: ERROR oslo_messaging.rpc.server File "/opt/stack/cinder/cinder/volume/drivers/lvm.py", line 470, in create_snapshot
Dec 25 14:25:02 SZX1000299228 cinder-volume[30425]: ERROR oslo_messaging.rpc.server snapshot['volume_name'],
Dec 25 14:25:02 SZX1000299228 cinder-volume[30425]: ERROR oslo_messaging.rpc.server File "/usr/local/lib/python2.7/dist-packages/oslo_versionedobjects/base.py", line 774, in __getit
Dec 25 14:25:02 SZX1000299228 cinder-volume[30425]: ERROR oslo_messaging.rpc.server return getattr(self, name)

```

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/529993
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=7ccfb2c8d94824321d4bfca7266c5d72674c061f
Submitter: Zuul
Branch: master

commit 7ccfb2c8d94824321d4bfca7266c5d72674c061f
Author: TommyLike <email address hidden>
Date: Mon Dec 25 09:19:20 2017 +0800

    Validate volume status again when snapshot created

    In a multitask environment, the volume can be deleted
    after the snapshot record is created. Add the validation
    right after the creation to avoid undeletable snapshot.

    Closes-Bug: #1739995

    Change-Id: Icbe86473243871996483fdc96c079b8861bac2e5

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/pike
Review: https://review.openstack.org/530964

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/530964
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=78cd77edef1a08f0472b8df0409adebb9b12e865
Submitter: Zuul
Branch: stable/pike

commit 78cd77edef1a08f0472b8df0409adebb9b12e865
Author: TommyLike <email address hidden>
Date: Mon Dec 25 09:19:20 2017 +0800

    Validate volume status again when snapshot created

    In a multitask environment, the volume can be deleted
    after the snapshot record is created. Add the validation
    right after the creation to avoid undeletable snapshot.

    Closes-Bug: #1739995

    Change-Id: Icbe86473243871996483fdc96c079b8861bac2e5
    (cherry picked from commit 7ccfb2c8d94824321d4bfca7266c5d72674c061f)
    Conflicts:
     cinder/tests/unit/api/v3/test_snapshots.py
     cinder/tests/unit/volume/test_volume.py

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/cinder 12.0.0.0b3 development milestone.

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/cinder 11.1.0 release.