NSX|P: Fix Octavia pool create with no listener

Change-Id: I1235272bae70f027ef1782786964bb35a4a67930

vmware_nsx/services/lbaas/nsx_p/implementation/pool_mgr.py

@@ -114,7 +114,7 @@ class EdgePoolManagerFromDict(base_mgr.NsxpLoadbalancerBaseManager):
 
         # NOTE(salv-orlando): Guard against accidental compat breakages
         try:
-            listener = pool['listener'] or pool['listeners'][0]
+            listener = pool.get('listener') or pool.get('listeners', [])[0]
         except IndexError:
             # If listeners is an empty list we hit this exception
             listener = None
@@ -166,7 +166,8 @@ class EdgePoolManagerFromDict(base_mgr.NsxpLoadbalancerBaseManager):
             description = new_pool['description']
         # NOTE(salv-orlando): Guard against accidental compat breakages
         try:
-            listener = new_pool['listener'] or new_pool['listeners'][0]
+            listener = (new_pool.get('listener') or
+                        new_pool.get('listeners', [])[0])
         except IndexError:
             # If listeners is an empty list we hit this exception
             listener = None