Bug description: modrdn2reple (retrocl_po.c) sets the given mods
to the changelog entry with "changes" attribute type if it includes
modifiersname, modifytimestamp, creatorsname, createtimestamp. When
the modrdn is internally initiated and passed mods do not include
the attributes (modifiersname, etc.), make_changes_string returns
empty lenstr. There were 2 issues:
1) there was nothing to add if lenstr was empty, but it was added.
2) there was a bug to set the length +1 even though the length was 0.
1) If there is nothing to add to the change attribute, skip calling
2) Remove adding "+1" for '\0' from the value length: val.bv_len.