When installing additional rpcd modules, a restart of rpcd is required.
This often confuses users as even after installing rpcd-mod-rpcsys the
relevant ubus objects are still missing until rpcd has been reloaded
(or the system has been rebooted, obviously).
Let rpcd-mod-* reload rpcd as post-install action.
Signed-off-by: Daniel Golle <daniel@makrotopia.org>