[MDC-873] simetbox-openwrt-simet-lmapd init: fix some permissions

[MDC-873] simetbox-openwrt-simet-lmapd init: fix some permissions

On boot, ensure /etc/simet/lmap/* are readable.  This fixes insanity
caused by a too-restrictive umask in rpcd leaking to simet-register-ma.

The real issue has been since fixed in simet-ma, but it might have left
a few devices with 0600 permissions in /etc/simet/lmap/*