mod_pubsub_serverinfo: Update to use mod_server_info (fixes #1841) ...but only for Prosody trunk users, because 0.12 mod_server_contact_info does not use the new API in mod_server_info.

2c07bcf56a36d6e74dc0f5422e89bd61f4d31239 0.8-diverge
1656d4fd71d07aa3a52da89d4daf7723a555e7dd last-google-code-commit