ISSUE-483: data race in ci test

[sijie]

Original Issue: apache#483

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WARNING: DATA RACE
Read at 0x00c00e4bfca8 by goroutine 499:
  github.com/apache/pulsar-client-go/pulsar.(*partitionConsumer).requestGetLastMessageID()
      /pulsar-client-go/pulsar/consumer_partition.go:279 +0x27e
  github.com/apache/pulsar-client-go/pulsar.(*partitionConsumer).internalGetLastMessageID()
      /pulsar-client-go/pulsar/consumer_partition.go:270 +0xea
  github.com/apache/pulsar-client-go/pulsar.(*partitionConsumer).runEventsLoop()
      /pulsar-client-go/pulsar/consumer_partition.go:802 +0x2cb

Previous write at 0x00c00e4bfca8 by goroutine 524:
  github.com/apache/pulsar-client-go/pulsar.(*partitionConsumer).grabConn()
      /pulsar-client-go/pulsar/consumer_partition.go:970 +0x1875
  github.com/apache/pulsar-client-go/pulsar.(*partitionConsumer).reconnectToBroker()
      /pulsar-client-go/pulsar/consumer_partition.go:883 +0x2db
  github.com/apache/pulsar-client-go/pulsar.(*partitionConsumer).runEventsLoop.func2()
      /pulsar-client-go/pulsar/consumer_partition.go:787 +0xbe

Goroutine 499 (running) created at:
  github.com/apache/pulsar-client-go/pulsar.newPartitionConsumer()
      /pulsar-client-go/pulsar/consumer_partition.go:208 +0xf46
  github.com/apache/pulsar-client-go/pulsar.newReader()
      /pulsar-client-go/pulsar/reader_impl.go:105 +0x8ab
  github.com/apache/pulsar-client-go/pulsar.(*client).CreateReader()
      /pulsar-client-go/pulsar/client_impl.go:152 +0xcb
  github.com/apache/pulsar-client-go/pulsar.TestReaderLatestInclusiveHasNext()
      /pulsar-client-go/pulsar/reader_test.go:571 +0x90d
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:909 +0x199

Goroutine 524 (running) created at:
  github.com/apache/pulsar-client-go/pulsar.(*partitionConsumer).runEventsLoop()
      /pulsar-client-go/pulsar/consumer_partition.go:780 +0x174
==================

https://github.com/apache/pulsar-client-go/pull/474/checks?check_run_id=1998557674

There is a data race happens when running the ci test. It happens occasionally