Bug 1538 Fixed

In case if df is not available in an NSD then  nsd.get("df", [[]])[0].get("vnf-profile", ())
raises an exception. Since [[]][0] returns a list and list does not have a get() function.
Fix is to change [[]] to [{}] such that when [{}][0] is executed we get a dict instead of
list.

Change-Id: I7e7ce62a44720dcc368ce7a4fa3d0bc1d7beb43b
Signed-off-by: K Sai Kiran <saikiran.k@tataelxsi.co.in>