Fix PHP-426 test for mongod 2.5.x

Querying system.users is not reliable since the server API changes in 2.5.x. Instead, we can simply query a collection to test if the connection was successfully established.
Fix PHP-629 test for mongod 2.5.x

Use buildInfo command instead of evaluating "db.version()" JavaScript. On 2.5.x, users require explicit permission to evaluate JavaScript.

Use of the "timeout" option is irrelevant here, in light of bug00683.phpt and mongoclient-ctor-002.phpt.