dirmngr: Fix build with no LDAP support.
* dirmngr/server.c [USE_LDAP] (start_command_handler): Conditionalize.
Cherry-pick master commit of:
7011286ce6e1fb56c2989fdafbd11b931c489faa
- GnuPG-bug-id: T6239
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>