recreate streams temp dir before start monitors

Working with in the raspberry pi, tmpfs dir /dev/shm/streams is unexpectly deleted and when monitor is restarting, it crash because streams directory does not exist.

Uncaught Exception occured!
Error: watch /dev/shm/streams/k8sGnHG8D2/iGRp0t995x/ ENOENT
    at _errnoException (util.js:992:11)
    at FSWatcher.start (fs.js:1382:19)
    at Object.fs.watch (fs.js:1408:11)
    at launchMonitorProcesses (/home/pi/Shinobi/camera.js:3488:64)
    at Timeout._onTimeout (/home/pi/Shinobi/camera.js:3431:29)
    at ontimeout (timers.js:498:11)
    at tryOnTimeout (timers.js:323:5)
    at Timer.listOnTimeout (timers.js:290:5)

This patch check that s.dir.streams exist before start any one monitor.