tests: Allow cassandra binary path to be configured through env variable
The current hard-coded value won't work for other distributions not relying on standard conventions (e.g. nixos...).
This keeps the original behavior and only allow to diverge based on the environment variable BIN_CASSANDRA [1] This also:
- fixes an issue on log path inexistence which raises.
- renames the other env variable LOG_CASSANDRA to SWH_CASSANDRA_LOG (for consistency)
Note: Currently trying to run this with my nixos box and this minimum prevents it.
Test Plan
tox
Migrated from D3505 (view on Phabricator)