Add support for cinder NFS snapshots

Add CinderNfsSnapshotSupport parameter that controls whether cinder's
NFS driver supports snapshots. The default value is True.

Depends-On: I4df8e3941eb074339e399e5a5c44fa411ff21560
Change-Id: I9a42f805fd28fd04bee771cac63bd0080b39c7c0

puppet/services/cinder-volume.yaml

@@ -52,6 +52,12 @@ parameters:
       NFS servers used by Cinder NFS backend. Effective when
       CinderEnableNfsBackend is true.
     type: comma_delimited_list
+  CinderNfsSnapshotSupport:
+    default: true
+    description: >
+      Whether to enable support for snapshots in the NFS driver. Effective
+      when CinderEnableNfsBackend is true.
+    type: boolean
   CinderNasSecureFileOperations:
     default: false
     description: >
@@ -159,6 +165,7 @@ outputs:
             tripleo::profile::base::cinder::volume::cinder_enable_rbd_backend: {get_param: CinderEnableRbdBackend}
             tripleo::profile::base::cinder::volume::nfs::cinder_nfs_mount_options: {get_param: CinderNfsMountOptions}
             tripleo::profile::base::cinder::volume::nfs::cinder_nfs_servers: {get_param: CinderNfsServers}
+            tripleo::profile::base::cinder::volume::nfs::cinder_nfs_snapshot_support: {get_param: CinderNfsSnapshotSupport}
             tripleo::profile::base::cinder::volume::nfs::cinder_nas_secure_file_operations: {get_param: CinderNasSecureFileOperations}
             tripleo::profile::base::cinder::volume::nfs::cinder_nas_secure_file_permissions: {get_param: CinderNasSecureFilePermissions}
             tripleo::profile::base::cinder::volume::iscsi::cinder_lvm_loop_device_size: {get_param: CinderLVMLoopDeviceSize}

releasenotes/notes/add-cinder-nfs-snapshot-support-16664aa46a67a5ad.yaml

@@ -0,0 +1,13 @@
+---
+features:
+  - |
+    Add new CinderNfsSnapshotSupport parameter, which controls whether
+    cinder's NFS driver supports snapshots. The default value is True.
+upgrade:
+  - |
+    Cinder's NFS driver does not support snapshots unless the feature is
+    explicitly enabled (this policy was chosen to ensure compatibility with
+    very old versions of libvirt). The CinderNfsSnapshotSupport default value
+    is True, and so the new default behavior enables NFS snapshots. This
+    change is safe because it just enables a capability (i.e. snapshots)
+    that other cinder drivers generally provide.