fifottl/limfifottl/utubettl: API for restarting TTL fiber

[oleg-jukovec]

Now the TTL fiber can stop and there is no way to restart it without an instance restart:

queue/queue/abstract/driver/fifottl.lua

Lines 165 to 167 in 3bfd1e2

	log.error("error catched: %s", tostring(err))
	log.error("exiting fiber '%s'", fiber.name())
	return 1