Remove drivers from tests

[gravis]

Tests are currently launched with make test, which will load a bunch of drivers, and try to execute basic operations with them.
As the number of drivers will grow over time, we should not rely on them to test this lib. The tests should be launched with go test ./... only, so no more docker containers with all the DBs.
Each driver will be responsible for its own test suite, and that's the good place to use containers.