paging_test: use function to check protocol v5 support
paging_test: use function to check protocol v5 support

patch by Jay Zhuang; reviewed by Jason Brown for CASSANDRA-14601

aweisberg/cassandra-dtest,pauloricardomg/cassandra-dtest,blerer/cassandra-dtest,stef1927/cassandra-dtest,iamaleksey/cassandra-dtest,aweisberg/cassandra-dtest,blerer/cassandra-dtest,iamaleksey/cassandra-dtest,pauloricardomg/cassandra-dtest,stef1927/cassandra-dtest,bdeggleston/cassandra-dtest,bdeggleston/cassandra-dtest,pcmanus/cassandra-dtest