Create unit test for topicLookup failure handling

[cornelk]

follow up from #14

=== RUN   TestClientTopics
log.go:184: TestClientTopics 2021/10/01 01:08:52 conn.go:72: *** Sending command: type:CONNECT connect:<client_version:"Pulsar Go 0.01" auth_method_name:"" protocol_version:15 >
log.go:184: TestClientTopics 2021/10/01 01:08:52 client.go:407: *** Received command: type:CONNECTED connected:<server_version:"Pulsar Server" protocol_version:15 max_message_size:5242880 >
log.go:184: TestClientTopics 2021/10/01 01:08:52 conn.go:72: *** Sending command: type:PARTITIONED_METADATA partitionMetadata:<topic:"persistent://public/default/topic-qinMLiUv" request_id:1 >
log.go:184: TestClientTopics 2021/10/01 01:08:52 client.go:407: *** Received command: type:PARTITIONED_METADATA_RESPONSE partitionMetadataResponse:<request_id:1 response:Failed error:MetadataError message:"Policies not found for public/default namespace" >
log.go:184: TestClientTopics 2021/10/01 01:08:52 conn.go:72: *** Sending command: type:LOOKUP lookupTopic:<topic:"persistent://public/default/topic-qinMLiUv" request_id:2 authoritative:false >
log.go:184: TestClientTopics 2021/10/01 01:08:52 client.go:407: *** Received command: type:LOOKUP_RESPONSE lookupTopicResponse:<response:Failed request_id:2 error:MetadataError message:"org.apache.pulsar.broker.web.RestException: Policies not found for public/default namespace" >
log.go:184: TestClientTopics 2021/10/01 01:08:52 client.go:401: Processing received command type:LOOKUP_RESPONSE lookupTopicResponse:<response:Failed request_id:2 error:MetadataError message:"org.apache.pulsar.broker.web.RestException: Policies not found for public/default namespace" >  failed: %!w(*errors.errorString=&{topic lookup response not supported: Failed})
log.go:184: TestClientTopics 2021/10/01 01:09:22 client.go:407: *** Received command: type:PING ping:<>
log.go:184: TestClientTopics 2021/10/01 01:09:22 conn.go:72: *** Sending command: type:PONG pong:<>
log.go:184: TestClientTopics 2021/10/01 01:09:52 client.go:407: *** Received command: type:PING ping:<>
log.go:184: TestClientTopics 2021/10/01 01:09:52 conn.go:72: *** Sending command: type:PONG pong:<>
log.go:184: TestClientTopics 2021/10/01 01:10:22 client.go:407: *** Received command: type:PING ping:<>