fix show interface neighbor expected empty issue (sonic-net#2465)

Author: jcaiMR

show/interfaces/__init__.py

@@ -307,9 +307,9 @@ def expected(db, interfacename):
             body.append([interfacename,
                          device,
                          neighbor_dict[interfacename]['port'],
-                         neighbor_metadata_dict[device]['lo_addr'],
-                         neighbor_metadata_dict[device]['mgmt_addr'],
-                         neighbor_metadata_dict[device]['type']])
+                         neighbor_metadata_dict[device]['lo_addr'] if 'lo_addr' in neighbor_metadata_dict[device] else 'None',
+                         neighbor_metadata_dict[device]['mgmt_addr'] if 'mgmt_addr' in neighbor_metadata_dict[device] else 'None',
+                         neighbor_metadata_dict[device]['type'] if 'type' in neighbor_metadata_dict[device] else 'None'])
         except KeyError:
             click.echo("No neighbor information available for interface {}".format(interfacename))
             return
@@ -320,9 +320,9 @@ def expected(db, interfacename):
                 body.append([port,
                              device,
                              neighbor_dict[port]['port'],
-                             neighbor_metadata_dict[device]['lo_addr'],
-                             neighbor_metadata_dict[device]['mgmt_addr'],
-                             neighbor_metadata_dict[device]['type']])
+                             neighbor_metadata_dict[device]['lo_addr'] if 'lo_addr' in neighbor_metadata_dict[device] else 'None',
+                             neighbor_metadata_dict[device]['mgmt_addr'] if 'mgmt_addr' in neighbor_metadata_dict[device] else 'None',
+                             neighbor_metadata_dict[device]['type'] if 'type' in neighbor_metadata_dict[device] else 'None'])
             except KeyError:
                 pass