Skip tests that require a database if we can't connect to one (#2413)
Skip tests that require a database if we can't connect to one (#2413)

* Skip tests that require a database if we can't connect to one

* Add `DENDRITE_SKIP_DB_TESTS` environment variable to bring @kegsay joy

* Call it `DENDRITE_TEST_SKIP_NODB` intead
matrix-org/dendrite,matrix-org/dendrite,matrix-org/dendrite,matrix-org/dendrite