Add NFS backend configuration option in salt-formulas/cinder project.

Add an ability to congfigure NFS (Network File System) for OpenStack Cinder.
Patch allows to set nfs_snapshot_support, nas_secure_file_operations
and nas_secure_file_permissions in reclass model and provide it to Cinder.

Related-Prod: PROD-17997 (PROD:17997)
Change-Id: Ie3715d28ab582fab6a72f897c22c62c6e64f5a44
diff --git a/cinder/files/backend/_nfs.conf b/cinder/files/backend/_nfs.conf
index 26e8e66..8d82497 100644
--- a/cinder/files/backend/_nfs.conf
+++ b/cinder/files/backend/_nfs.conf
@@ -9,3 +9,16 @@
 nfs_mount_point_base = {{ backend.get('path', '/mnt') }}
 nfs_shares_config = /etc/cinder/nfs_shares_{{ backend_name }}
 nfs_sparsed_volumes = True
+
+{%- if backend.nas_secure_file_operations is defined %}
+nas_secure_file_operations = {{ backend.nas_secure_file_operations }}
+{%- endif %}
+
+{%- if backend.nas_secure_file_permissions is defined %}
+nas_secure_file_permissions = {{ backend.nas_secure_file_permissions }}
+{%- endif %}
+
+{%- if backend.nfs_snapshot_support is defined %}
+nfs_snapshot_support = {{ backend.nfs_snapshot_support }}
+{%- endif %}
+