Elytron caching-realm backed by ldap-realm should avoid hitting LDAP for a cache hit

Elytron caching-realm backed by ldap-realm provides caching for identity objects but not for related credentials and attributes. This is currently due to design of ldap-realm (like in case of filesystem-realm, see JBEAP-8628).

Credentials and attributes should not be loaded from LDAP for a cache hit.

Blocks EAP7-542 Elytron Caching Support. Note: caching of credentials is not a requirement, but may be reconsidered and become an enhancement to overall performance, see analysis document of the RFE. However, jdbc-realm is designed to enable caching of credentials. To be consistent, the ldap-realm should also enable caching of credentials.