Fix the --net option to gnt-instance add

Similar to the --disk fixes a while ago, --net is broken too. This patch
fixes it.

Reviewed-by: imsnah

scripts/gnt-instance

@@ -321,7 +321,7 @@ def AddInstance(opts, args):
     except ValueError, err:
       raise errors.OpPrereqError("Invalid NIC index passed: %s" % str(err))
     nics = [{}] * nic_max
-    for nidx, ndict in opts.nics.items():
+    for nidx, ndict in opts.nics:
       nidx = int(nidx)
       nics[nidx] = ndict
   elif opts.no_nics: