Section 'Persistence' in 'luci-app-mosquitto' is unusable without 'persistence'
section in config file.

Signed-off-by: Ptilopsis Leucotis <PtilopsisLeucotis@yandex.com>

This should always have been available in the mosquitto package itself.
This file needs to exist in basic form to allow the init scripts to even check whether it exists.

Signed-off-by: Karl Palsson <karlp@etactica.com>