ITS#9420 - Fix memory leak in modrdn

Fix provided by grapvar@gmail.com
3 jobs for its9420 in 32 minutes and 46 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #2873
build-gnutls-mit-standalone-lloadd

00:31:12

passed #2871
build-no-threads-no-slapd

00:03:20

passed #2872
build-openssl-heimdal-lloadd

00:32:46