Further fix cqlsh_copy_tests on Windows
Further fix cqlsh_copy_tests on Windows

We need to use NamedTemporaryFile(delete=False) on Windows to prevent
access violations. Also cleaned up CqlshCopyTester.tearDown logic on
Windows and for calling super.tearDown in general.

thobbs/cassandra-dtest,carlyeks/cassandra-dtest,iamaleksey/cassandra-dtest,beobal/cassandra-dtest,krummas/cassandra-dtest,mambocab/cassandra-dtest,aweisberg/cassandra-dtest,bdeggleston/cassandra-dtest,stef1927/cassandra-dtest,snazy/cassandra-dtest,blerer/cassandra-dtest,beobal/cassandra-dtest,krummas/cassandra-dtest,carlyeks/cassandra-dtest,bdeggleston/cassandra-dtest,spodkowinski/cassandra-dtest,iamaleksey/cassandra-dtest,stef1927/cassandra-dtest,pcmanus/cassandra-dtest,spodkowinski/cassandra-dtest,riptano/cassandra-dtest,snazy/cassandra-dtest,riptano/cassandra-dtest,mambocab/cassandra-dtest,pauloricardomg/cassandra-dtest,thobbs/cassandra-dtest,aweisberg/cassandra-dtest,pauloricardomg/cassandra-dtest,blerer/cassandra-dtest