CP-311125 unhide AD cache pool parameters in XE CLI

[lindig]

External authentication using Active Directory can use a cache to improve performance. The corresponding fields on the pool object so far were hidden. This patch makes them visible, and as a consequence more easily accessible from the CLI and its autocompletion.

[lindig]

File "ocaml/libs/xapi-stdext/lib/xapi-stdext-threads/dune", line 35, characters 33-47:
35 |   (names threadext_test ipq_test scheduler_test)
                                      ^^^^^^^^^^^^^^
(cd _build/default/ocaml/libs/xapi-stdext/lib/xapi-stdext-threads && ./scheduler_test.exe)
{Scheduler}
ASSERT ratio is 1.104465
make: *** [Makefile:60: test] Error 1

This looks unrelated to the code here.