entrypoint wait-for-it misconfigured - it will start regardless of the state of other containers

Currently the graylog container implements the wait-for-it script on startup, checking that opensearch etc... has started. Currently it will start the graylog container regardless of the state of the target container after the 15 second wait time.

The readme from the wait-for-it script mentions that this is expected behaviour, and that to turn give it a blocking function you need to add the --strict flag:

> The subcommand will be executed regardless if the service is up or not. If you wish to execute the subcommand only if the service is up, add the --strict argument.