Enable support for Lightning Memory-Mapped Database Manager (LMDB)

[fbrehm]

Since 389-ds-base 2.1.0, The 389 ldap directory server supports two kind of underlying database:

• Berkeley Database (BerkeleyDB)
• Lightning Memory-Mapped Database Manager (LMDB)

Starting from version 3.0.0 New instances are no longer created with BerkeleyDB by default but with LMDB.

See FAQ about BerkeleyDB backend deprecation and using LMDB backend.

For 389-ds-base >= 2.1.0 and < 3.0.0 the resource ds_389::instance should provide an option for selecting the database engine. For this in creation of the template file for the instance in section [slapd] there should be a key/value pair with the key 'db_lib' and a value of either 'bdb' (BerkeleyDB) or 'mdb' (LMDB). The default value should be 'mdb'.