The ldb library path seems incorrect as it does not work in the built-in
ldb of Samba 4.22. Fix that by using SAMBA_LDB_MODULESDIR. This should
fix the following runtime error:
```
* (2025-12-02 03:12:12): [sssd] [sysdb_ldb_connect] (0x4000): No ldb module path set in env
* (2025-12-02 03:12:12): [sssd] [sysdb_ldb_connect] (0x4000): No ldb module path set in env
* (2025-12-02 03:12:12): [sssd] [ldb] (0x0010): WARNING: Module [memberof] not found - do you need to set LDB_MODULES_PATH?
```
Also, use SAMBA_IDMAP_MODULESDIR for consistency.
PR: 291492
Approved by: portmgr blanket
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D54138
75d3ee66bb