package/paho-mqtt-c: bump to version 1.3.5

This is a paho-mqtt-c maintainace release. It fixes some memory leaks as
well as a potential deadlock:

https://github.com/eclipse/paho.mqtt.c/milestone/8?closed=1



Signed-off-by: Julien Grossholtz <julien.grossholtz@openest.io>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>