api: reload ruledb on updating objectgroups

previously they only contained metadata (name/comment) so for the
rulesystem that was not relevant. Now with the attributes and/invert
we want to reload the ruledb on update too.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
[S.I.: fix typo in commit subject]
Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>