lldpd: Init config read on reload

lldpd: Init config read on reload

Init script reload with trigger to detect config file update.
Reload command added to attempt non-impactful lldpd reload where
lldpcli can be used to update config without process restart.
Config hash function used to track whether process restart is needed.

Signed-off-by: Stephen Howell <howels@allthatwemight.be>
(cherry picked from commit e483c247dc75723a32d03b5b1149f7fd61ac8ac6)
Link: https://github.com/openwrt/openwrt/pull/15299
Signed-off-by: Robert Marko <robimarko@gmail.com>