options_validate: add ClientUseIPv4 unit tests and update other unit tests

legacy/trac#17076 (moved) adds unit tests for options_validate. It's been merged to master.

legacy/trac#17840 (moved) adds ClientUseIPv4 and ClientPreferIPv6DirPort, and changes the meaning of other options. It was based off pre-#17076 master.

This ticket is for updating the unit tests after legacy/trac#17840 (moved) merges.