first round of SHADOW flags/isupdate test unification

servers/slapd/back-bdb/add.c

servers/slapd/back-bdb/delete.c

servers/slapd/back-bdb/modrdn.c

servers/slapd/back-ldap/add.c

servers/slapd/back-ldap/modify.c

servers/slapd/back-ldbm/add.c

servers/slapd/back-ldbm/delete.c

servers/slapd/back-ldbm/modrdn.c

servers/slapd/backend.c

servers/slapd/overlays/rwm.c

servers/slapd/proto-slap.h

servers/slapd/slap.h