fix read_only property not plumbed through tosca
diff --git a/xos/tosca/resources/xosmodel.py b/xos/tosca/resources/xosmodel.py
index 86aa8a8..343fb1f 100644
--- a/xos/tosca/resources/xosmodel.py
+++ b/xos/tosca/resources/xosmodel.py
@@ -17,7 +17,7 @@
 class XOSVolume(XOSResource):
     provides = "tosca.nodes.XOSVolume"
     xos_model = XOSVolume
-    copyin_props = ["host_path"]
+    copyin_props = ["host_path", "read_only"]
     name_field = "container_path"
 
     def get_xos_args(self, throw_exception=True):