cql-pytest: add a couple of default-TTL tests
cql-pytest: add a couple of default-TTL tests

This patch adds a new cql-pytest test file - test_ttl.py - with
currently just a couple of tests for the "with default_time_to_live"
feature. One is a basic test, and second reproduces issue #9842 -
that "using ttl 0" should override the default time to live, but
doesn't.

The test for #9842, test_default_ttl_0_override, fails on Scylla and
passes on Cassandra, and is marked "xfail".

Refs #9842.

Signed-off-by: Nadav Har'El <625169824b719df98706d88646d0aae6f368ae4d@scylladb.com>
Message-Id: <20211227091502.553577-1-625169824b719df98706d88646d0aae6f368ae4d@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla