Camera: Remove thread that keeps HAL service alive for extra delay

hwservicemanager now guarantees clients will be held for ~5s before the
callback onClients(false) is called and they are allowed to exit.

Test: On walleye_svelte, manually observe camera behavior and the
      lifetime of the lazy camera service process.

Change-Id: Iafbdd73f439da3a4f0fecb069e356d30aa2732b5