Fix test cases with tablets and without

[dkropachev]

They use same function that is called only once, if you pass tabletsDisabled = true first time and second time with tabletsDisabled = false.
You are going to get keyspace without tablets anyways

func createSessionFromClusterHelper(cluster *ClusterConfig, tb testing.TB, tabletsDisabled bool) *Session {
	// Drop and re-create the keyspace once. Different tests should use their own
	// individual tables, but can assume that the table does not exist before.
	initOnce.Do(func() {
		createKeyspace(tb, cluster, "gocql_test", tabletsDisabled)
	})

	cluster.Keyspace = "gocql_test"
	session, err := cluster.CreateSession()
	if err != nil {
		tb.Fatal("createSession:", err)
	}

	if err := session.control.awaitSchemaAgreement(); err != nil {
		tb.Fatal(err)
	}

	return session
}