Refactor/restructure glance cinder store

This is an effort to decouple some of the cinder backend specific
code (like nfs, scaleio) from the generic logic.
The purpose is to make the code modular and any change
for a particular cinder backend should not affect the code path
of other backends thereby reducing regression.
This is also required for another use case of supporting extend
of attached volumes added in [1].
Following are the major changes done in this patch:

1) Move cinder store to a new directory 'cinder' and rename
   'cinder.py' to 'store.py' (similar to swift)
2) Create new files for nfs and scaleio backends for moving code
   specific to these backends into their own separate file.
   This also fixes one bug when using sparse files in nfs and
   we wait for file size to be equal to volume size (initially done
   for scaleio/powerflex backend) but this will never happen for
   nfs sparse files. See bug: 2000584
3) Move cinder tests to 'tests/unit/cinder' directory and add tests
   for base, nfs and scaleio files.
4) Modify/fix existing tests

Closes-Bug: #2000584

[1] https://review.opendev.org/c/openstack/glance_store/+/868742

Depends-On: https://review.opendev.org/c/openstack/glance/+/869021

Change-Id: I26c272b6c503e98fbbafca411d3eec47283bd6fc

1 files changed, 5 insertions, 0 deletions

diff --git a/releasenotes/notes/cinder-fix-nfs-sparse-vol-create-76631ce05f86257c.yaml b/releasenotes/notes/cinder-fix-nfs-sparse-vol-create-76631ce05f86257c.yaml
new file mode 100644
index 0000000..c80f420
--- /dev/null
+++ b/releasenotes/notes/cinder-fix-nfs-sparse-vol-create-76631ce05f86257c.yaml
@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    `Bug #2000584 <https://bugs.launchpad.net/glance-store/+bug/2000584>`_:
+    Fixed image create with cinder NFS store when using sparse volumes.