Switch away from using rpc_endpoint=8091 and back to 8090 which is trillian_log_server's default.
This simplifies the commands to start trillian log_server, reducing it down to:
trillian_log_server --logtostderr ...
and avoids diverging from upstream when there is no need.

This change also updates the corresponding docker-compose and k8s configs.

Signed-off-by: axelsimon <github@axelsimon.net>