Bug 2160 fixed: verifying if VDUR exists within the method update_ns_vld_target

Change-Id: I2f3ce8a8b32a2bc72e5e3022dd88c120300e2b29
Signed-off-by: Pedro Escaleira <escaleira@av.it.pt>
(cherry picked from commit aa366ed3)

osm_lcm/ns.py

@@ -840,6 +840,8 @@ class NsLcm(LcmBase):
                         None,
                     )
                     vdur = next((vdur for vdur in target_vnf.get("vdur", ())), None)
+                    if not vdur:
+                        return
                     for a_index, a_vld in enumerate(target["ns"]["vld"]):
                         target_vld = find_in_list(
                             get_iterable(vdur, "interfaces"),