created separate 'image_name' field to allow user to specify desired VM through TOSCA;
if 'default' used for 'image_name', will use slice's default image

Change-Id: I2cc286c91915fdb8ca24c949ad25255841b8c15f
diff --git a/xos/synchronizer/steps/sync_vmmetenant.py b/xos/synchronizer/steps/sync_vmmetenant.py
index 19a2782..f494e1e 100644
--- a/xos/synchronizer/steps/sync_vmmetenant.py
+++ b/xos/synchronizer/steps/sync_vmmetenant.py
@@ -49,6 +49,6 @@
     def get_extra_attributes(self, o):
         fields = {}
         fields['tenant_message'] = o.tenant_message
-        #vmmeservice = self.get_vmmeservice(o)   #not needed cause there's no service message 
+        fields['image_name'] = o.image_name
         return fields