Allow configure cinder with the nfs driver

This patch allow to use nfs as cinder driver.

To use it, in the localrc we can now set

CINDER_DRIVER=nfs
CINDER_NFS_SERVERPATH=172.16.0.50:/export_cinder

The nfs-server is not setup by devstack.

Change-Id: I8e240d00b58f272d04ab2c0922c551b1f7266260
diff --git a/lib/cinder b/lib/cinder
index f6f137c..cab8b6e 100644
--- a/lib/cinder
+++ b/lib/cinder
@@ -281,6 +281,11 @@
             iniset $CINDER_CONF DEFAULT xenapi_nfs_server "$CINDER_XENAPI_NFS_SERVER"
             iniset $CINDER_CONF DEFAULT xenapi_nfs_serverpath "$CINDER_XENAPI_NFS_SERVERPATH"
         )
+    elif [ "$CINDER_DRIVER" == "nfs" ]; then
+        iniset $CINDER_CONF DEFAULT volume_driver "cinder.volume.drivers.nfs.NfsDriver"
+        iniset $CINDER_CONF DEFAULT nfs_shares_config "$CINDER_CONF_DIR/nfs_shares.conf"
+        echo "$CINDER_NFS_SERVERPATH" | sudo tee "$CINDER_CONF_DIR/nfs_shares.conf"
+        sudo chmod 666 $CINDER_CONF_DIR/nfs_shares.conf
     elif [ "$CINDER_DRIVER" == "sheepdog" ]; then
         iniset $CINDER_CONF DEFAULT volume_driver "cinder.volume.drivers.sheepdog.SheepdogDriver"
     elif [ "$CINDER_DRIVER" == "glusterfs" ]; then