Test "auth_source_ldaps" API paths

Flesh out the `AuthSourceLDAP` class and add this class to module
`test_multiple_paths`. Reference bugzilla bug 1140313 ("Cannot read an auth
source ldap's host via the API") in the updated test suite.
Merge pull request #1340 from Ichimonji10/test-auth-source-ldaps

Test "auth_source_ldaps" API paths