Trim down test_multiple_paths.py

Make all all tested entities (i.e. classes in entities.py) inherit from
`EntityReadMixin`. Take advantage of this fact to trim down module
`test_multiple_paths`.

Add a logger to module `test_multiple_paths`. Log out information in several
tests, thus allowing the assertions to be trimmed down.
Merge pull request #1343 from Ichimonji10/test-multiple-paths

Trim down test_multiple_paths.py
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.