ITS#3847 silence warnings

servers/slapd/ad.c

servers/slapd/back-bdb/init.c

servers/slapd/back-ldbm/modrdn.c

servers/slapd/back-ldbm/search.c

servers/slapd/backend.c

servers/slapd/cancel.c

servers/slapd/config.c

servers/slapd/controls.c

servers/slapd/cr.c

servers/slapd/ctxcsn.c

servers/slapd/entry.c

servers/slapd/modify.c

servers/slapd/operation.c

servers/slapd/repl.c

servers/slapd/schema_init.c

servers/slapd/sl_malloc.c

servers/slapd/starttls.c