fix flaky test in SnapshotServiceFactoryBeanIntegrationTest

[CharlesZKQ]

In org.springframework.data.gemfire.snapshot.SnapshotServiceFactoryBeanIntegrationTest, the test handleArchiveFileLocation() is flaky due to the non-deterministic property of java.io.File.listFiles() (please refer document). I fixed it by sorting the array of File for both the expectedSnapshots and actualSnapshots, which eliminates the flakiness of this test.