Compat redis 120

I'm following up on https://github.com/PerlRedis/perl-redis/issues/65. It's an ubuntu 10.04-LTS system, so not really that old and it has the "LTS" in its name which stands for long term support. So it may be worthwhile to adjust the test suite a little to have at least a certain percentage of all tests passing. Compared to running the tests manually and deciding whether installation is safe, this should provide more confidence to users on such a system.

Besides, this exercise found a bug in t/tlib/Test/SpawnRedisServer.pm. A missing local() on $? caused action at a distance on that ubuntu machine: all test runs that killed redis server, returned a status of 15. Consequently Test::Builder decided that 15 was the wrong value and considered all these tests as failed. It's not clear to me why this bug was not triggered on other machines, maybe I'm missing something. But the small change in commit 17d9eacd fixed it on ubuntu and did not break it on my debian setup.

I'd be delighted if you could accept this pull request.

Thanks for your considerations,