auth_base: 36 new tests

$ ./run_tests tests/plugins/auth/auth_base.js 
Running tests:  [ 'tests/plugins/auth/auth_base.js' ]

auth_base.js
✔ hook_capabilities - no TLS, no auth
✔ hook_capabilities - with TLS, auth is offered
✔ get_plain_passwd - get_plain_passwd, no result
✔ get_plain_passwd - get_plain_passwd, test user
✔ check_plain_passwd - valid password
✔ check_plain_passwd - wrong password
✔ check_plain_passwd - null password
✔ select_auth_method - no auth methods yield no result
✔ select_auth_method - invalid AUTH method, no result
✔ select_auth_method - valid AUTH method, valid attempt
✔ auth_plain - params type=string returns OK
✔ auth_plain - params type=empty array, returns OK
✔ auth_plain - params type=array, successful auth
✔ check_user - bad auth
✔ check_user - good auth
✔ hook_unrecognized_command - AUTH type FOO
✔ hook_unrecognized_command - AUTH PLAIN
✔ hook_unrecognized_command - AUTH PLAIN, authenticating
✔ hexi - hexi

OK: 36 assertions (1146ms)