recovery: Don't automount external storage at startup

 * Do it for hotplug and on-demand only.

Change-Id: I9c0ca96203a8ff1f16fa42e31f426cd25bdaba1d
recovery: Add sdcard daemon

 * Our custom ext4 support for sdcards needs it.

Change-Id: Ie1c22c1d6a3255cbe3a7ff3c072243f4a5461a17