Do a metadata refresh after an explicit metadata write.

if we have a template with (logically) the following:
instance2:
   metadata
     GetAtt waitcond.data

waitcond:

when the waitcond is fired, it updates the metadata but it needs a call
to update the references in "instance2's" metadata.

bug #1135229
Signed-off-by: Angus Salkeld <asalkeld@redhat.com>
Change-Id: I1a6af9112ba100b17075063f59165b448d6a11f4