Spring-session: Improve Hazelcast client-server topology integration tests

[vpavic]

Instead of providing Hazelcast server config via system properties in our client-server topology integration tests, we could simplify things by copying config file to default location thus overriding the default one provided in the container.

This will also help us with adopting to changes from testcontainers/testcontainers-java#1814, that are preventing us to upgrade to Testcontainers 3.12.1+.

[bsideup]

@vpavic wait... did https://github.com/testcontainers/testcontainers-java/pull/1814 break your code? o_O

It was supposed to be a backward-compatible change and, if it did, it sounds like a regression! 😨

[vpavic]

Yep, I've just left a comment there.